This paper is focused primarily on the current capabilities of the CRD100 subsea robotic drilling platform. An overview is given of the available hardware and interface approach. Time analysis of our wireline system over conventional drilling is included. Reasoning for several design decisions are provided. Aspects of the interface and its semi-automated hierarchical control system of Ethernet distributed pressure tolerant electronics (PTE) I/O modules are presented. The discussion includes explanation of several ‘lessons learned’ that have been encountered over several years of off-shore drilling experience. From these we have determined that the method of human control of the remote subsea robotic drill should be performed by two operators simultaneously. A pilot chooses what they want to control, be it the drill, its arms, the thrusters or the legs and their co-pilot chooses a complementary set of controls. Data from factory acceptance tests are used to demonstrate how well two operators expedite the procedure. Although we strive to automate as many aspects of the drilling operation as practical, we show that at present two competent operators (assisted by automated processes) drive the system more efficiently than one. The wireline system has greatly reduced the time to acquire core samples compared to conventional drilling techniques. Further, we have developed this system so that core barrels may be exchanged for scientific probes, such as the cone penetration test (CPT), without the need for conventional trip out. Our system was implemented with the first subsea PTE that operates over Ethernet. Using distributed PTE has reduced the costs of controlling subsea robotic equipment, both in cost of the electronics housings and cabling, while improving data collection. The paper discusses the use of several of these PTE in a hierarchical control system. The applications of our drill to the petroleum industry is primarily in the exploration and ground analysis for off-shore construction. The approach of using robotic sea floor drills is a means to avoid the expense of employing drill ships for geotechnical exploration.

Abstract Deepsea mining sites are usually large areas of polymetallic nodules or seafloor massive sulfide (SMS) deposits. Prior to underwater mining campaigns, successful exploration programs have to be taken into account in order to include selection of target areas by means of seafloor and sub-seafloor surveys of the rocks and sediments. Coring of the submarine sediments plays a major role for evaluating of the marine sediments and they are useful for future mining operations. The main geology which hosts the polymetallic nodules is pelagic clay. On the seafloor and specifically at the mudline, this kind of soils has very low undrained shear strength up to 20 kPa. In order to properly design the nodule harvester, which will be in contact with the sea floor, physical properties of the seabed and shallow subsurface (i.e. the upper 100–200m)are needed to compute bearing capacity. Underwater soil cores can be used to evaluate soil type, cohesion, unit weight of soil, modulus of elasticity. Seafloor massive sulfide (SMS) deposits are very different from the polymetallic nodules. In this case, cores are needed in order to assess possible anomalies. Measured uniaxial compressive strength (UCS) values strengths in the SMS zone can be very high. Drill cores are required for assessing the mineral content at these deposits. The MeBo200 is a sea bed drill rig presently developed by the MARUM Center for Marine Environmental Sciences at the University of Bremen and the department of Maritime Technologies of BAUER Maschinen GmbH. It is well suited for core drilling in formations of comparable strength and therefore it is suitable preparatory geotechnical exploration. MeBo200 is the second generation of MeBo. From 2008 to 2012 MeBo was employed in 9 expeditions. 66 deployments took place in up to 2,050 m water depth. 1,445 m were cored in different type of geologies, concentrating more on the quality of the cores. These include crystalline rocks from the Porcupine Bank west of Ireland, as well as very soft homogenous silty clays in the Gela Basin with very low undrained shear strength values. The recovery rate was good for hard rocks and cohesive soft sediments. Taking into account the case histories of MeBo it is possible to state that for underwater mining applications the new MeBo200 can be utilized for geological and geotechnical drilling campaigns.

Japan Agency for Marine-Earth Science and Technology (JAMSTEC) is developing a unique wireline retrievable coring tool for sampling of rocks below the deep sea floor. This tool is mainly composed of a turbine motor, a piston/cylinder, an inner tube. A cutting shoe at the bottom of the inner tube is rotated at high speed by the turbine motor and it trims cores. The advantage of applying the turbine motor is that the coring with high rotating speed and low weight on bit is possible compared with conventional coring and it is expected to be effective to improve the core recovery rate and core quality especially for hard fractured rock or interbedded hard / soft formations. This paper presents outline of this tool and several test results on shore.

JAMSTEC has an international patent for the environmentally-friendly cultivation system of hydrothermal chimney as the accessory product of scientific drilling program in the Okinawa Trough. We introduce the characteristics of natural and artificial hydrothermal vents in the Okinawa Trough, how this field was developed with special devices in the IODP Exp. 331, and new findings which lead to black ore cultivation system. The topography around the hydrothermal vent was not flat surface in which conventional drilling guidebases cannot be used. A special guidebase, capable of inclinations up to 30 deg, was required for surface coring. The other challenge is the continuous flow from the hydrothermal vent whose maximum fluid temperature excessed 300 °C. Our research plan was to drill and cut the core through the guidebase, and set casing pipe and wellhead cap to collect pristine hydrothermal fluid by ROV. The drilling and coring were successfully conducted through the guidebase deployed at 1000 mbsf (meter below sea floor). The retrieved core had high content of H 2 S gases which imposed us to wear breathing apparatus. Due to the high flow rate of 300 °C hotwater, the conventional bitumen core liners rapidly disintegrated. The hotwater producing from the top of wellhead cap has been vigorous with high flow rate in at least two years. The most remarkable finding was the highly rapid growth of sulfide chimney mainly composed of sphalerite, chalcopyrite and galena. After 25 months from the drilling, this sulfide chimney whose metal grade is higher than that of black-ore on land has grown to be 15 m in height. A new development plan was initiated to aim the cultivation of the chimney and efficient ore recovery. A custom-ordered cultivation tree attached to the wellhead cap is currently being developed. JAMSTEC is planning to have the future expedition to launch the cultivation system at the Okinawa Trough for existing and additional wellhead. This expedition will focus on cultivation of the black ore from hydrothermal vent. The future planning of this project is also discussed in this paper.

Abstract As a part of the offshore production test program, in June and July of 2012, Japan Oil, Gas and Metals National Corporation (JOGMEC) conducted coring operation in the Eastern Nankai Trough where the first offshore production test of methane hydrates was to be conducted. By using a pressure coring device, Hybrid PCS developed by Japan Agency of Marine Science and Technology (JAMSTEC), Aumann and Associate Inc. (AAI), and JOGMEC, pressure conserved cores were recovered from methane hydrate-bearing sandy formations although some technical difficulties encoutered. The samples were analyzed onboard by Pressure Core Analysis and Transfer System (PCATS, GeoTek). Some samples were sent to onshore laboratories for further analyses. Continuous 60m intervalin a methane hydrate concentrated zone was cored and fairly good core recovery and pressure conservation rates were achieved. The obtained data are used for reservoir characterization of methane hydrate concentrated zone from where gas was produced during the actual production test conducted in March 2013.

Abstract Any intervention into the seafloor will have an impact on the structural integrity of the material in the affected region and will hence result in variation in stress, pore water pressure, and temperature. As a consequence fluids maybe mobilized and may in turn affect the intervention process. To closely track such processes or monitor safe operations in areas of e.g. hydrocarbon exploitation, seafloor mining or marine renewables, new measuring strategies have to be developed to allow a spatio-temporal coverage via a sensor network. With the deep-sea drill MARUM-MeBo that has been developed at the University of Bremen/MARUM new opportunities are opened up to deploy sensors in shallow boreholes (<80 m sub-seafloor depth). MeBo is characterized by its versatility and high mobility with deployments down to water depths of 2000 m. Materials recovered via wire-line coring technique included both soft sediments and hard rocks. After drilling a 2.35 m section the core is recovered using a wire that is latched to the inner core barrel with an overshot. The outer drill string stays in the drilled hole during the entire drilling process. Recently, simple self-contained borehole instruments were developed that are placed in the hole, in which the outer drill string serves as casing. We propose to employ MeBo to deploy a network of instrumented boreholes in the region of deep-sea interventions to monitor the environmental conditions continuously over long time intervals. Data can be exchanged via acoustic modems and may serve to archive time series and use in hazard assessment and early warning.

Abstract The detection and measurement of migrated hydrocarbons in near-surface marine sediments is a relatively routine exploration method to investigate issues of hydrocarbon charge. The presence of near-surface migrated thermogenic hydrocarbons provides strong evidence that an active petroleum system is present, as well as critical information on source, maturity and migration pathways. There are multiple methods currently applied by industry to collect, prepare, extract, and analyze migrated hydrocarbons within near-surface marine sediments. To improve the detection of seabed thermogenic hydrocarbon seepage, core samples should be collected along likely major migration pathways (cross stratal leakage features) identified by conventional deep seismic and high-resolution seafloor imaging technology. Real time imaging provides greater detail to confirm targeted features for more precise core targeting. Not all targeted cores will hit the designated feature and thus collecting replicates along major migration features is critical. Collecting sediment samples below the Zone of Maximum Disturbance (ZMD) to avoid possible transition zone alteration effects and recent organic matter (ROM) masking problems is critical. Choosing a coring device best suited for local seabed conditions will maximize both penetration and sediment recovery. Multiple sections per core should be collected at variable depths providing a geochemistry profile. Geochemical analysis should include a full range of hydrocarbon types; hydrocarbon gases (C1 to C5), gasoline plus range hydrocarbons (C5 to C12), and high molecular weight hydrocarbons (C12+). Two types of geochemistry samples should be collected; one to capture the volatile light hydrocarbons (C1 to C12) and non-hydrocarbon gases; and a second for the higher molecular weight hydrocarbons (C12+). The light hydrocarbons require special handling and containers to limit volatile loss and prevent post sampling microbial alteration. Bulk sediment measurements such as quantity of organic matter and sand percent can provide additional important non geochemical information. Identification of background versus anomalous populations is critical when evaluating sub-surface migrated seabed hydrocarbons. Sediment hydrocarbons are normally highly altered and may not resemble conventional reservoir oil. Novel petroleum related hydrocarbon compounds need to be examined to fully evaluate organic maturity and source facies. Mapping thermogenic hydrocarbon seeps (oil and gas) relative to key cross-stratal migration pathways via fluid flow modeling and seismic attribute analysis provides an effective petroleum systems tool to better understand the near-surface petroleum relative to subsurface hydrocarbon generation and entrapment. Bear in mind not all surface geochemical surveys will result in the detection of statistically valid thermogenic hydrocarbon seepage.

Abstract The ROVDrill Mk.2 is a state-of-the-art seabed push sampling, rotary coring andin situ testing system designed for working in 2500m water depth and obtaininggeotechnical data to a depth of 120m below seabed. The system has beendeveloped as a geotechnical upgrade to two ROVDrill subsea robotic drillingsystems previously utilised in rotary coring mode in deep-water for the seabedmining industry. The paper considers the key design features of the current generation of subseadrill rigs and contrasts some of the key conceptual design differences betweenthem. A brief case study looking at the evolution of the ROVDrill Mk.2 rig ispresented including discussion of some of the technical upgrades and an outlineof its principal specifications. A number of benefits of seabed drilling are highlighted, with particular regardto working in deep water and harsh environments. With the elimination of humanexposure to pipe and tool handling risks, improved operational efficiency andsample quality and increased borehole depth accuracy, the development of seabedpush sampling, rotary coring and in situ testing systems are attractive to theoffshore site investigation market and a real alternative to traditional drillships. A Brief History of Subsea Drilling Technology Subsea drilling equipment began to appear in commercial use in the 1970's. Theearliest examples of these units were diver operated, marinized terrestrialsingle-shot rotary diamond core drilling rigs used for shallow rock coring forsurvey purposes. They also found application installing the small diameterpiles which are used to restrain and stabilize oil and gas pipelines in shallowwater zones with rocky seabeds, such as those found in the Persian Gulf and NWAustralia coastal oilfields. During the last 25 years or so, in step with the marine industry move to deeperwater beyond diver depths and taking advantage of increasingly standardized andsophisticated ROV control technology, subsea drill rigs have become remotelyoperated. Early examples remained as single-shot rotary coring systems, butmore capable rigs were developed initially for the deep-water scientific rockcoring research community. As the technology matured more sophisticated drillrig functionality was developed such as subsea pipe storage racks, iron-roughnecks/foot-clamps for pipe make/break, drill/grout mud pumps andcomplete monitoring and surveillance systems. Since 1996 a number of heavier duty subsea drill rigs have been built for usein the both geological research and commercial subsea geotechnical market. These units are of higher power (up to 150HP) and are capable of drillinglarger diameter bores (typically in the range 50mm to 75mm core diametercapability) and to greater depth (from 20m to over about 100m) than previousrigs. Systems targeting the geotechnical market additionally feature as aminimum push sampling (i.e. sampling of uncemented soils) and cone penetrationtesting (CPT) capabilities.

Abstract Activities surrounding the commercial exploration and extraction of seafloor massive sulfide (SMS) deposits have been gaining stronger momentum over the last 3-4 years; the most widely publicized being the successful geophysical and geotechnical SMS exploration campaigns being executed in licensed tenements in the territorial waters off Papua New Guinea. Most recently, in late 2010, a 100 day SMS geotechnical drilling program commenced in the " Solwara?? SMS deposit fields, some 50km off the coast of the Papua New Guinea mainland in water depths of up to 2000m. The program included a target total sample recovery of 3000m of core to be used for mineral grade assaying and a series of 10-20m geotechnical bore holes to assist with seabed mining tool design verification. The somewhat physically challenging nature of the seabed topography in this area in terms of gradient and composition has had to be addressed and overcome by the development and implementation of innovative technical solutions and operational processes and procedures, in order to ensure a successful campaign. Therefore a specially designed remotely operated seafloor drilling and down-hole sampling rig was selected, complimented by a fully integrated surface support vessel spread, including a purpose built and optimized core handling and processing system onboard. This paper will describe the technical aspects of the seafloor drilling solution and discuss in detail; the methods, merits and advantages of the fully integrated technical and operational solution and will further present and discuss examples of actual drilling data and productivity performance indicators. Introduction Nautilus Minerals has located Seafloor Massive Sulfide (SMS) deposits on various Exploration Licenses that it holds within the Territorial Waters of Papua New Guinea. Solwara 1 is the first site Nautilus intends to commercially develop and is located approximately 50 km north of Rabaul in the eastern extent of the Bismarck Sea, New Ireland Province, Papua New Guinea. The Solwara 1 deposit occurs on a small ridge on the NW flank of the North Su volcanic centre. The water depth across the Solwara 1 site ranges nominally from 1,450m to 1,700m and the deposit is characterized by a series of sulfide-rich mounds that occur along a small volcanic ridge on the NW side of the volcano. Clusters of copper-rich sulfide ‘chimney’ structures reaching sometimes to approximately 15 m high above the sea floor occur as outcrops on top of these mounds. Some of the chimneys are actively discharging hot hydrothermal fluids into the water column. However, most of the chimney structures are inactive. Chimney fragments and unconsolidated fine-grained sediments occur between the chimney outcrops. The cover sediments thicken in low-lying areas and around the edges of the deposit. Based on the analysis of previous geophysical survey and geotechnical sampling and drilling campaigns undertaken on this and other adjacent deposits, it has been strongly inferred by both Nautilus Geologists and independent competent consultants that beneath the sediment cover, the mounds generally consist of a thin layer, several meters thick - however, comprising semi-lithified sediment (in places containing sulfide chimney fragments). The semi-lithified sediment layer is underlain by the main massive to semi-massive sulfide lens (dominantly chalcopyrite and pyrite), which is estimated to be several meters to >20 m thick in places. This main sulfide unit also contains minor zones of sulphate-breccias (anhydrite, barite), with possible cavities in places. The main sulfide unit is underlain by strongly altered volcanic rocks containing a high proportion of clays. The altered volcanics pass into fresh, unaltered (glassy) volcanic rocks, particularly around the boundaries of the deposit.

Abstract Nautilus Minerals is the world leader in exploration and development of deep ocean seafloor massive sulphide (SMS) resources. The company is currently focused on generating its resource pipeline in the Western Pacific and its first development project for recovery of high-grade copper, gold and silver mineralisation from its Solwara 1 site in the Bismarck Sea, Papua New Guinea. The Solwara 1 site is located at a water depth of 1,600 - 1800 meters. Over 150 SMS seafloor surface samples have been collected from chimney structures during dives made by remote operated vehicles (ROVs). In order to obtain an understanding of the sub-surface mineralisation, Nautilus carried out 3 drilling programs between 2006 and 2008 which allowed the calculation of a Canadian NI43-101 compliant resource estimate. The initial 2006 campaign was based on conventional offshore surface driven drill equipment. In conjunction with the subsea remote technology industry, Nautilus subsequently developed an ROV operated seafloor drill system with improved drill core recovery and efficiency. This technology was developed further with a 2010 drill program to increase the available geological knowledge at Solwara 1 and adjacent prospects. This paper will provide an overview of Nautilus' SMS drilling requirements and recap the evolution of drilling technology and operations undertaken at Solwara 1 from 2006 to 2010. The paper will also discuss the potential of further developments in drilling techniques and equipment to increase or improve drilling depth, efficiency and data quality. Introduction Nautilus Minerals is a leader in the exploration and development of Seafloor Massive Sulphide (SMS) systems. These high grade copper, gold and zinc deposits are considered to be modern analogues of ancient volcanogenic massive sulphide (VMS) deposits. In the western Pacific, Nautilus Minerals is predominantly engaged in exploration for SMS systems in the territorial waters of Papua New Guinea and the 1887 Proclamation Area of Tonga. Nautilus Minerals development plan is to commence production at its Solwara 1 site located within Mining Lease (ML) 154 in the Bismarck Sea, Papua New Guinea. As of January 2011, the Solwara 1 prospect has a NI 43-101 compliant indicated and inferred mineral resource estimate of 870 kT and 1,300 kT respectively. SMS systems are typically located in water depths greater than 1,000 metres and in close proximity to tectonic plate boundaries and submarine volcanic activity. Cold seawater which has entered the earth's crust is heated to high temperatures by volcanic and magmatic processes, forming hot hydrothermal fluids, which can become rich in economic metal concentrations. These hot fluids are driven to the seafloor by convection, producing hydrothermal plumes or " black smokers??. SMS systems are formed by the precipitation of metal bearing sulphide minerals as chimneys, which range from mere decimetres to a few metres in diameter and can reach up to 20 metres in height. The continued process of chimney build-up, extinction, renewal and collapse can lead to the formation of sulphide mounds, which can be hundreds of metres in lateral extent (Figure 1).

Abstract A new deepwater static cone penetrometer system, " CPT Stinger??, was used to investigate subsurface conditions at a number of production sites in the deepwater Gulf of Mexico. Same site high-resolution geophysical data and long cores obtained with a Jumbo Piston Core (JPC) system illustrate the excellent correlation obtained with continuous geotechnical and geophysical data for defining the spatial variation in soil properties. The high cost of drilling deepwater borings and sampling at widely spaced intervals imposes a significant constraint on obtaining a sufficient quantity of high quality soils data. Thus, improved methods are desirable for more quickly assessing requisite soil properties without sacrificing accuracy. The " CPT Stinger?? system is a new tool that can fill this role. This new system allows the same general suite of JPC coring equipment to be modified for CPT testing and can be deployed from an oilfield supply vessel. By simply replacing the standard piston core liner with a CPT system containing thrusting rods, a power/control module, and CPT data logging system, the field operation can quickly be converted from sampling to in situ testing mode. The results show that the new system provides continuous soundings with centimeter-depth accuracy and stratigraphic consistency. In addition to the acquisition of high-quality static CPT data, the sampling rate of the CPT logger allows the acquisition of dynamic CPT data during free fall that can be adjusted for velocity differences to emulate static data A particularly effective way to use the system is in conjunction with nearby, continuous sampling with JPC cores and subbottom seismic profiles. This allows the correlation of the CPT results with strengths from continuous samples over a significant depth of overlap and with the geophysical cross sections. Correlations are presented in the paper for undrained shear strength data from long cores with insitu CPT data. Following the premise that more information acquired for a given budget tends to reduce the risks associated with foundation design and installation planning, the economic benefits of rapidly acquiring the geotechnical data from a lower cost vessel are also discussed. Introduction The high cost of deepwater oil and gas developments has focused much attention on fast tracking these projects from discovery to production. An integrated geologic/geotechnical study including the " CPT Stinger?? system provides an opportunity to characterize subsurface conditions in a cost effective manner. In contrast, the high cost of drilling deepwater rotary borings that sample at widely spaced intervals tends to limit the opportunity to acquire a sufficient quantity of high quality soils data to fully understand the site. Background The importance of conducting integrated geoscience (geologic/geotechnical) studies for deepwater developments has been clearly described by Campbell et al. (1988)1 and Young and Kasch (2011)2. The three-dimensional integrated geoscience (geologic/geotechnical) model must be defined early to serve as a basis for planning the architecture of production facilities. The model serves to better understand the constraints imposed by: geologic conditions and geo-hazards, subsurface stratigraphy and its spatial variability, and variable soil profiles and geotechnical properties. The resulting goal of the integrated geoscience model is to select facility sites with favorable conditions such as those with uniform geologic/geotechnical conditions and those most conducive to safe operations of planned seafloor supported structures.

Abstract This paper describes the pressure coring and pressure core analysis tools to be used on the upcoming Gulf of Mexico Joint Industry Project (GOM-JIP) Expedition III. Pressure cores and pressure core analysis have become more important as scientists, exploration geologists, and geohazard engineers strive to understand gas-rich formations, including but not limited to gas-hydrate-bearing marine sediments, coalbed methane reserves, and shale gas reservoirs. After the highly successful GOM-JIP logging-while-drilling Expedition II, gas-hydrate-rich sections have been identified and will be cored on GOM-JIP Expedition III. Extensive use of pressure coring tools is anticipated, providing both samples for laboratory studies as well as data collected under pressure for the scientific community. The new HPTC (High Pressure Temperature Corer) will collect 3.5-meter-long samples of core at in situ pressures, while the one-meter-long FPC and FRPC (Fugro Pressure and Rotary Pressure Corers) will be used as alternate coring systems. All coring tools will be adapted to work in a flexible bottom hole assembly negating any need to trip pipe between changes of tools. PCATS (Pressure Core Analysis & Transfer System) will provide the infrastructure to both handle and conduct non-destructive testing of all these cores under pressure, providing gamma density, ultrasonic P-wave velocity, and X-ray computed tomography (CT) of the cores at full pressure. PCATS moves cores under pressure with linear and rotational precision for use with other purpose-built, compatible measurement systems and also cuts subsections of core under pressure, pushing these pieces into customized pressure cells for further analysis and testing. It is anticipated that together these four tools will collect and provide to the scientific community more pressurized core samples from GOM-JIP Expedition III than from all previous gas hydrate expeditions. Introduction The Gulf of Mexico Joint Industry Project (GOM-JIP) has completed two gas hydrate drilling expeditions and is preparing for a third. This upcoming expedition is focused on gas-hydrate-bearing sands, which have been identified in the logging-while-drilling (LWD) data from GOM-JIP Expedition II. The collection of pressure core data to verify and ground truth the LWD data is a major goal of GOM-JIP Expedition III. An intensive pressure coring program is being planned to achieve these goals. Pressure cores are vital to gas hydrate studies as they preserve gas hydrate and the sedimentary structures in which it forms, allowing geophysical studies of the sediment-hydrate matrix as well as quantitative estimates of hydrate concentration. In non-pressurized core, gas hydrate dissociates during or soon after core recovery as a result of decreasing pressure and increasing temperature. The dissociation of gas hydrate creates large volumes of gas that expand and often destroy the complete fabric of the core prior to it reaching the surface. Cores recovered at or near in situ hydrostatic pressures and temperature preserve the contents for detailed analysis in the laboratory.

Abstract FSCL has just completed an exploratory borehole to determine the suitability of ground conditions for the development of the world's first offshore salt cavern gas storage scheme. The facility, for a UK developer, is a series of sub-surface caverns, to be created in the salt strata below the Irish Sea and when built (subject to planning consent and financing), will substantially improve the security of energy supply for the UK and Irish Markets. The paper will review the detailed planning, project risks and bespoke equipment that was needed to produce excellent, 100 mm diameter core recovery down to 865 meters below the seabed. Site investigations to circa 1000 meters below the seabed are possible and cost effective solutions can be offered against the need for oilfield drill rigs. Excellent core recovery can be achieved in salt strata and can be combined with a detailed testing programme to give a total picture of the strata investigated. This may open the door to development of future offshore salt cavern facilities. The return of 100mm core for the full depth of the borehole allowed direct correlation of the site with other land based salt strata core samples. The core samples correlated well with the downhole testing programme data and the result provided detailed characterisation of the geology investigated. The site investigation has provided the necessary information to design the salt storage caverns and moved the project forward from a possibility to a reality. The design of the gas storage caverns has commenced and the cavern construction programme is planned to start in 2010. The caverns will provide an initial working gas capacity of 1,200 million cubic meters, and the storage facility will substantially improve the security of energy supplies for the UK and Irish markets. Introduction In August 2007 FSCL undertook an exploration borehole for Gateway Storage Company Limited (" Gateway??) in the Morecombe Bay area of the Irish Sea. The purpose of the borehole was to establish the feasibility of using the underlying salt beds as an area for gas storage in solution mined caverns. This was only the second offshore site considered worldwide. The British Government has set the highest priority on increasing gas storage capability in the United Kingdom.

Abstract Marine gas hydrate investigations, whether they be conducted as resource evaluations for national governments, as geohazard assessments for major oil companies, or as climate-related scientific endeavors funded through international funding agencies, have begun to develop common strategies. Gas hydrate can occur up to several hundred meters below the sediment-water interface, depending on the water depth and thermal gradients; consequently, for a full assessment of gas hydrate occurrence, nature, distribution, and concentration, samples must be obtained through drilling and coring. Samples retrieved and analyzed at full in-situ pressures using pressure coring techniques are the only way to ground truth the findings from other techniques, including physical and chemical analysis of non-pressure cores or the interpretation of seismic and borehole log data. Thermal imaging of non-pressure cores provides an immediate and valuable method for observing the endothermic behavior of dissociating gas hydrate but does little in itself to characterize the gas hydrate morphology or concentration. Porewater analysis techniques rely on the freshening of porewaters when gas hydrate dissociates, generally measured via chlorinity; these analyses provide excellent spot measurements of the concentration of gas hydrate if the background chlorinity profile is well established, but tells the investigator little about the nature of the gas hydrate. Furthermore, in lakes or nearshore environments where the porewaters may have very low or highly variable chlorinities, this technique will be far less reliable or accurate. Only methane mass balance calculations from depressurization of cores recovered at full pressure provides the benchmark or " gold standard?? for gas hydrate concentration assessment. Measurements of the density and volume of pressure cores through X-ray imaging and gamma densitometry have removed errors in estimation of pore volume, making this methane mass balance technique accurate and robust. Non-destructive testing and analysis of gas-hydrate-bearing cores at in-situ pressures and temperatures also provides detailed information on the in-situ nature and morphology of gas hydrate in sediments. The detailed profiles of density and VP, together with spot measurements of Vs, electrical resistivity, and hardness, provide background data essential for modeling the behavior of the formation on a larger scale. X-ray images show the hydrate morphology in relation to the sediment, which will control the kinetics of methane release. Gas-hydrate-bearing pressure cores subjected to X-ray tomographic reconstruction provide compelling evidence that gas hydrate morphology in many natural sedimentary environments is particularly complex and impossible to replicate in the laboratory.

Abstract Piston corers are commonly used for the recovery of unconsolidated marine sediment samples. Compared to straight push tube samplers, they offer an improved potential to recover higher quality, longer core samples, particularly where coarse-grained marine sediments are being investigated. There are a number of different types of piston corers deployed in geotechnical site investigations today - ranging from traditional free fall, single stroke, mechanically triggered devices to much more sophisticated, seabed-deployed, or alternatively down-hole vessel-deployed, devices. The Hydraulically Tethered Piston Corer (HTPC) described in this paper is deployed down a borehole using a seabed founded, remotely operated drill rig. The design characteristics of this tool are described, together with the operating methodology. A number of studies, which assess the quality of the samples recovered using this tool are presented. The results demonstrate the high quality of the sample achieved with this device compared to other sampling techniques. Triaxial tests, undertaken to assess sample disturbance, indicate that the samples can be classified within the ‘very good to excellent’, ‘good to fair’ categories as defined by NGI (the Norwegian Geotechnical Institute). Thin section fabric analyses indicate that very little sample disturbance has occurred at the sample margin, and no disturbance has occurred elsewhere within the samples. Recent literature has suggested that a larger sample diameter is perhaps the most critical factor in recovering undisturbed samples for geotechnical testing. However, the results presented herein demonstrate that the quality of the samples is perhaps more greatly influenced by careful consideration of tool geometry during tool design, together with precise control of the tool during the sampling process. Introduction Piston coring is a widely used methodology for reliably obtaining near continuous marine sediment samples in materials ranging from very soft fine grained sediments commonly encountered in deepwater sites and alluvial deltas, to the typically coarser grained sediments recovered from shallow water zones along continental shelves. Piston corers are differentiated from open-ended, push samplers by the inclusion of a tethered piston within the barrel. Both systems are equipped with a cutting shoe at the leading edge of the barrel and may be also equipped with a core catcher. Continuous sampling to full barrel capacity is possible for these devices provided: The bearing capacity of the soil ahead of the cutting shoe exceeds the mobilized soil/liner interface friction capacity and Sufficient thrust is available to overcome forces mobilized ahead of the cutting shoe, and friction/adhesion mobilized on the external surface of the barrel. Piston corers usually provide improved recoveries compared to conventional, open-ended, push corers. In an ideal system, the piston imparts a controlled ‘suction’ pressure to the top of the soil sample, whenever flow of soil into the barrel is impeded due to excessive interface friction between the liner and the soil. This effect is particularly beneficial where dilatant, coarse-grained soils are being sampled.

Abstract The centrifuge method to determine capillary pressure curves involves increasing the centrifugation speed in steps and measuring the amount of water expelled from a core plug at equilibrium. This approach requires the use of several assumptions related to the unknown fluid distribution in the core and gravity effects. It is also time consuming since only one point in the curve is obtained at each speed. The quantitative nature of the Double Half K-Space Single Point Ramped Imaging with T1 Enhancement Magnetic Resonance Imaging method makes it ideally suited for the measurement of fluid distribution in core plugs, thus reducing the number of speeds necessary to obtain a full capillary pressure curve. The Centrifuge-Magnetic Resonance Imaging method requires only the use of a moderate rotational speed centrifuge and an inexpensive low field permanent magnet. Capillary pressure curves were obtained for primary drainage, imbibition, and secondary drainage in water/oil systems. By establishing a free water level at half height of the core, negative capillary pressure data was obtained for imbibition and secondary drainage. Attention is necessary to the fluid redistribution when high permeability cores are tested. INTRODUCTION Capillary pressure curves for rocks are used to predict the potential hydrocarbon recovery from a reservoir. Traditional methods to determine these curves include mercury intrusion, porous plate, and centrifuge. Mercury intrusion is considered a rapid method, but it has limitations in providing information on reservoir wettability. Porous plate is a direct and accurate technique but it is time consuming since the equilibration time can be weeks or months for each pressure point. The centrifuge method (Hassler and Brunner, 1945) involves rotating a core plug at different speeds and allowing time for saturation equilibrium in the core at each speed. The amount of fluid expelled is measured at each speed and an average saturation in the core is determined. By using an approximate solution, Hassler and Brunner (1945) proposed a method to obtain the inlet saturation corresponding to the inlet capillary pressure. This solution makes the assumptions that the outlet face of the core remains 100% saturated with the wetting phase at all centrifugal speeds, and that the core length is negligible with respect to the radius of rotation. The SPRITE Magnetic Resonance Imaging method has proved to be a suitable technique to determine the capillary pressure curve of core plugs (Chen and Balcom, 2005, Chen et al., 2006, Green et al., 2007). To determine the capillary pressure with this technique, the distribution of the fluids along the length of the core is obtained without any of the assumptions required in traditional centrifuge testing. Better still this technique is directly quantitative compared to traditional, less quantitative, spin echo based MRI (Baldwin and Spinler, 1998). In this paper, we present the procedure to determine the capillary pressure curves in core plugs using Double Half K-Space Single Point Ramped Imaging with T1 Enhancement MRI, combined with a moderate speed centrifuge.

Abstract Recovery of cores and logging data from a dynamically positioned drill ship introduces significant heave related depth uncertainties. Heave compensation plays a pivotal role in assuring downhole data integrity by countering the effects of the ship's heave while tools are downhole. A linear displacement wireline heave compensation system has been in routine use on the D/V JOIDES Resolution since 1988. A rotary heave compensation system has been designed for the IODP recently to replace the linear unit. The new rotary unit consists of an electro-hydraulic winch, supporting position sensors, electronics and software to add and remove cable slack in response to ship heave. Analysis of acceleration logs recorded from downhole tools in both time and frequency domain compares the effectiveness of the linear and rotary heave motion compensators. Fourier amplitude spectra of uphole and downhole acceleration indicate that compensation reduces the heave influence on downhole acceleration by an order of magnitude for both compensation systems. These results are consistent for a variety of downhole tools, and suggest an average of 52-74% variance reduction in downhole acceleration for the linear system. Analysis of acceleration data with the rotary heave compensator system shows 75-80% variance reduction between the uphole and downhole spectra. Although these results are preliminary, our analysis shows comparable effectiveness of the rotary and linear compensation systems. Introduction Characterization of the dynamics of ship heave and its effect on logging and coring has long been a primary concern for the Deep Sea Drilling Projects (DSDP), the Ocean Drilling Program (ODP), and the Integrated Ocean Drilling Program (IODP) (e.g., Kidd, 1979; Francis, 1981; Goldberg, 1990). The difficulty in recovering deep-sea cores and logging data as far as 8 km below the sea surface from a floating ship presents significant uncertainties. The problem is particularly acute inrecovering cm-scale features, such as thin sediment bedding using downhole logs. During ODP, a wireline heave motion compensator (HMC) was designed and installed on the D/V JOIDES Resolution to reduce the effect of wave motion and ship heave on the position of downhole instruments on the wireline and core barrels. When the HMC is not operating, the acceleration of the downhole tool is primarily a function of the heave (vertical motion) of the ship, which mimics the uphole acceleration. When the HMC is operating, the downhole acceleration due to heave is minimized (Figure 1). At optimum efficiency, the compensator can reduce the variance of downhole acceleration by over 50% with an estimated downhole displacement of about 1.5 m (Goldberg, 1990). Controlled by on-board sensors which monitor the movement of the ship by recording ship motion, the HMCsystem integrates the acceleration twice to yield position (or heave) of the ship. Anticipating the needed compensation, a hydraulic cylinder connected to the wireline sheave is extended or retracted to adjust its position for ship heave. The cylinder moves in opposition of ship's heave.

Abstract Scientific ocean drilling programs such as the Deep Sea Drilling Project (DSDP, 1968-1983) and Ocean Drilling Program (ODP, 1985-2003) have pioneered the study of marine methane hydrates through the development and application of sampling tools, wireline measurements and other techniques used to characterize hydrate deposits along continental margins. These tools and techniques have evolved over many years of engineering development and field trials on multiple expeditions, which have been marked by strong collaborative efforts among academic and industry participants with support from government sponsors. This paper will describe the current status of some of these tools and measurement systems and discuss their potential use in global deepwater exploration of marine methane hydrate. Knowledge of the gas concentration in deep sediment is critical for understanding the dynamics of hydrate formation and the effect hydrates may have on the physical properties of the sediment. However, reliable data on gas concentration are difficult to obtain. The only way to determine true in situ concentrations of natural gas in the sub-seafloor is to retrieve cores in an autoclave chamber that maintains as closely as possible in situ conditions. Characterizing natural marine methane hydrate deposits helps to advance our understanding of these ubiquitous deposits and determine their role as a hazard to be avoided or a potential resource to be explored. Introduction To date, three dedicated scientific ocean drilling expeditions have been undertaken to advance our understanding of marine methane hydrates, namely, ODP Legs 164 (Blake Ridge and Carolina Rise; Ref. 1) and 204 (Hydrate Ridge, offshore Oregon; Ref. 2) and Integrated Ocean Drilling Program (IODP) Expedition 311 (Cascadia Margin, offshore Vancouver Island, Canada; Ref. 3). These dedicated expeditions, which served to sequentially advance the tools, methods and procedures used to study hydrate deposits, were highly successful because of strong collaborative efforts among engineers, scientists and technicians to develop, test and deploy new technologies in innovative ways. For example, closely spaced measurements of temperature made using thermistors inserted into sediment through plastic core liners during ODP Leg 164, evolved into continuous noninvasive measurements of thermal anomalies made using infrared thermal imaging cameras during ODP Leg 204. Similarly, the availability of a single tool for wireline pressure coring on ODP Leg 164 (Ref. 4), evolved into the use of multiple pressure coring tools on ODP Leg 204 due to the synergistic efforts of U.S., European and Japanese groups of engineers and scientists focused on similar research and development goals over several years (Ref. 5). These tools and techniques have coalesced into a set of integrated operational procedures that serve to provide a robust system for characterizing methane hydrates in their natural environment and in the laboratory onboard the JOIDES Resolution .

Abstract The Lake Malawi Drilling Project (LMDP) overcame many logistical and technical challenges to successfully drill and recover high quality, near continuous sediment cores from beneath one of the largest, deepest and most remote lakes in the world. Lake Malawi sediments contain a high resolution record of past climate in sub-Saharan Africa and the sediment cores obtained from the LMDP are being studied to reconstruct the climate history. The in-land location and the deep water (>600 m) conditions in Lake Malawi required mobilization of a dynamically positioned drilling vessel and a mobile coring system from Europe and North America. Major refit of a fuel barge resulted in a vessel that could hold station long enough to complete the drilling objectives through neardaily severe thunderstorms. After initial incompatibilities between the coring system and the drilling system, 616 m of high quality sediment cores were recovered from a total of 7 boreholes at two sites. The average core recovery at the two sites, excluding the first shakedown borehole, was 100%. Once split, the visual observation of the core sections showed excellent core quality with very little drilling disturbance. The excellent core quality enables scientific analyses of stratigraphy that represents changes in past climate. Introduction Lake and marine sediment deposits have long been an important source for studying the Earth's past climate. The sediments of Lake Malawi, located in the East African Rift valley, are ideally suited for high resolution climate studies. The regional sensitivity to climate variations, high lake sedimentation rates, and undisturbed lake bottom combine to create a high resolution annual to decadal climate record. The sediment age is directly related to the depth of the sediment beneath the lake floor. To obtain the past climate record over a long period of time, sediment must be recovered from deep beneath the lake floor. The goal of the Lake Malawi Drilling Program (LMDP) was to recover high quality, continuous sediment cores from below the lake floor in water depths ranging from 350m to 600m. Originally, four sites, shown in Figure 1, were proposed for drilling based on interpretations of high-resolution seismic reflection data (Scholz, 1999). Lake Malawi is one of the largest, deepest and most remote lakes of the world. Due to the in-land location of the lake, drillship mobilization for deep water drilling is impossible. Lake conditions are very susceptible to seasonal conditions. It was important to complete the drilling program within a predetermined weather window to minimize operational complications due to rough weather. Malawi is also considered one of the poorest nations of Africa (CIA, 2006) with limited infrastructure and resources. The drilling program required that a dynamically positioned drilling vessel be mobilized with the capabilities of station keeping, drilling and coring in deepwater. Technologies from the oil and gas industry and the geotechnical drilling and scientific communities were combined and adapted to successfully drill and recover core from two sites in Lake Malawi.

Abstract The Integrated Ocean Drilling Program (IODP) has developed an 8-1/4' instrumented drill collar with a 4-1/8' I.D. forroutine use in the programâ??s global coring program. An inductive data link to an instrumented core barrel has been added to acquire coring data in both core barrel and drill collar simultaneously while coring. The project consists of two independently engineered systems that interface downhole to exchange data and provide near real-time measurements made at the bit. The first component is the instrumented drill collar that measures weight-on-bit (WOB), torque-on-bit (TOB), annulus pressure, bore pressure, and annulus temperature at 1 Hz. The second component is the retrievable memory module which includes pressure and acceleration measurements and the data link system required to retrieve and store the data from the instrumented drill collar. The memory module can be fastened to the top of all standard IODP core barrels and will record the drilling dynamic data, while coring, via the inductive data link. The memory module and core barrel are returned to the rig floor using conventional wireline coring techniques which do not consume any additional rig time. Field testing has demonstrated that the concept is viable and that data can be reliably transmitted through the data link while coring. Introduction The Integrated Ocean Drilling Program has made a concerted effort over the last 10 years to collect more information from the BHA to quantify the dynamics at the drill bit while coring and drilling. This endeavor is critical to the retrieval of high quality core and to ensuring the highest recovery of core in a wide range of water depths and lithologies. Continuous coring in IODP holes is performed by recovering the core barrel at regular intervals, typically every 9.5 m. The procedure is the same for advanced piston coring (APC) in soft sediments, and for the rotary coring bit (RCB) in harder formations. An empty core barrel is deployed to the bottom hole assembly (BHA), latched into the BHA, then advanced 9.5 m during coring. The core barrel is then retrieved by a wireline retrieval system which latches to the top of the core barrel. After reaching the rig floor, the core is removed for analysis and an empty core barrel is dropped in the drill string to continue the coring process. IODP coring, drilling and logging operations occur without the use of riser and typically use sea water for circulation. Without a riser, measuring true depth between the kelly bushing and sea floor is complicated as there is no fixed reference to the sea floor. Accelerometers have historically been used to measure the ship motion, and through a double integration of the acceleration data, position could be estimated. The position data is critical in understanding ship's position relative to the bottom of the hole for maximum core recovery and core quality. The ODP and IODP have long utilized drill string heave compensation to counter the effects of ship heave on the cutting of core and the deploying of seafloor instruments.