Integrating Pressure Data From Formation Tester Tools and DSTs To Characterize Deepwater Fields, East Kalimantan, Indonesia
- Jack MacArthur (Unocal Indonesia Co.) | D.T. Vo (Unocal Indonesia Co.) | Steve Palar (Unocal Indonesia Co.) | Albert Terry (Unocal Indonesia Co.) | Trevor Brown (Unocal Indonesia Co.) | _ Hariyadi (Unocal Indonesia Co.) | Ron May (Unocal Indonesia Co.)
- Document ID
- Society of Petroleum Engineers
- SPE Reservoir Evaluation & Engineering
- Publication Date
- October 2001
- Document Type
- Journal Paper
- 437 - 450
- 2001. Society of Petroleum Engineers
- 3 Production and Well Operations, 1.1 Well Planning, 1.5 Drill Bits, 4.3.3 Aspaltenes, 4.6 Natural Gas, 2.4.3 Sand/Solids Control, 5.2 Reservoir Fluid Dynamics, 5.6.2 Core Analysis, 4.5 Offshore Facilities and Subsea Systems, 5.5.11 Formation Testing (e.g., Wireline, LWD), 1.8 Formation Damage, 4.1.5 Processing Equipment, 1.7.5 Well Control, 7.6.2 Data Integration, 4.2 Pipelines, Flowlines and Risers, 5.1.1 Exploration, Development, Structural Geology, 5.1.7 Seismic Processing and Interpretation, 5.6.1 Open hole/cased hole log analysis, 4.1.2 Separation and Treating, 2 Well Completion, 1.6.9 Coring, Fishing, 5.1.2 Faults and Fracture Characterisation, 4.6.2 Liquified Natural Gas (LNG), 1.2.3 Rock properties, 5.1.5 Geologic Modeling, 5.1 Reservoir Characterisation, 5.5 Reservoir Simulation, 4.3.4 Scale, 5.5.2 Core Analysis, 2.2.2 Perforating, 1.6 Drilling Operations, 5.6.4 Drillstem/Well Testing
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In the past 3 years, two significant commercial hydrocarbon accumulations inthe deep waters of the Makassar Strait, Indonesia, were discovered. Thesefields are located approximately 16 miles northeast of the giant Attaka fieldin 1,400 to 3,400 ft of water.
To date, more than 40 exploration and appraisal wells have been drilled inboth fields, and extensive pressure data have been collected by formationtester tools and drillstem tests (DSTs). The pressure data, used with otherdata such as seismic and well logs, have enabled us to characterize deepwaterturbidite sand reservoirs.
In this deepwater environment, DSTs are used selectively and only withstrong justification because of their prohibitive cost. Instead, the use of thepressure-testing tool is pushed to its limit to gain extensive data onpressure, rock, and fluid properties conventionally obtained by DSTs.
This paper will show how the deepwater reservoirs were characterized bymeans of pressure data from formation tester tools and DSTs to complementgeological and seismic data interpretations. Reservoir characteristics such asfluid type, fluid contacts, reservoir connectivity, and sand geometry can beinferred from the pressure gradients and pressure transients. These data areused in constructing reservoir fluid-flow models for a field-developmentplan.
Since the early 1990s, Unocal Indonesia Co. has been using a cost-effectivephilosophy in exploring and developing fields in the continental shelf of theMahakam delta, offshore East Kalimantan, Indonesia. Through the drill bits,their operations are specially designed to capture reservoir data in asufficient, cost-effective way by carefully selecting between wants and needswhile gathering data. Experience gained over the years from drilling toformation evaluation has resulted in the continuing refinement of the tools andtechniques involved in implementing these programs. As the company pushesexploration beyond the shelf into the deep water in this known hydrocarbonprovince, this cost-effective practice again provides the backbone forexploration.1
This paper presents a case study that demonstrates the integration of dataderived from different sources to characterize complex hydrocarbon-bearingreservoirs recently discovered in the deep water of the Makassar Strait,Indonesia. The key to understanding these reservoirs that led to Unocal'sapproved development plan stems from a cost-effective data-acquisition programthat focuses on extensive collection of reservoir data from formation tests.The paper describes how this abundant, less-expensive source of data is usedtogether with data from other sources, such as cores, seismic, logs, and DSTs,to characterize complex turbidite sandstone reservoirs. On the basis of thesedata, reservoir simulation models are constructed to forecast potential oil andgas recoveries and to drive the field-development plan. The methodology used inconstructing these models and key reservoir parameters that influence thedecision to select a specific plan of development are also discussed.
Deepwater Geology in the Makassar Strait
In 1996, Unocal Indonesia began its exploration program in Indonesia deepwater in the Makassar Strait, offshore East Kalimantan. Since then, twosignificant oil and gas accumulations, among others, have been discovered lyingin the deep water of this known hydrocarbon province. Located approximately 16miles east/northeast of Attaka field, these new fields are in water depthsranging between 1,400 and 3,400 ft (Fig. 1).
Hydrocarbon pays are found in the Pliocene and Upper Miocene stackedsandstone reservoirs deposited in the middle to upper slope setting ofsubmarine fan systems extended from the northern Mahakam delta (Fig. 2).Significant pays are also found deposited in the lower-slope, channel-levee,turbidite setting throughout the Miocene. At reservoir depths varying between4,000 and 12,000 ft subsea true vertical depth (ssTVD), hydrocarbonaccumulations are trapped structurally and/or stratigraphically by faulting,anticlinal rollover and/or pinchout. The Pliocene sandstones have a dominantstratigraphic trapping component. The channels are well defined, with trapsforming where the sandstones pinch out updip into impermeable shales or aresealed by normal faults. The Miocene traps are predominantly structural, withaccumulations, for the most part, located in structurally high positions on alarge faulted anticlinal feature. Faults in both the Pliocene and Miocene oftenact as lateral seals.
Typical pay thickness ranges from 200 to 400 ft net hydrocarbon pay, withindividual sand beds being a few feet to a few tens of feet in thickness, butbundled into reservoir intervals of tens to hundreds of feet thick. Sandstonesin the Pliocene and Miocene are quartzitic and predominantly fine-grained.However, sandstones ranging from very fine to coarse-grained have beenencountered at different levels across the fields. The grains are normallysubrounded to subangular and moderately well sorted. Average porosities rangefrom 24 to 32%, with permeabilities in the 10- to 1,000-md range.
Use of Wireline-Conveyed Formation Tester Tools
Before the introduction of the Modular Dynamic Tester (MDT**)tool,2 the traditional Repeat Formation Tester (RFT**) tool was usedto obtain pressure data and to identify formation fluid. Although the pressuremeasurement could be observed in real time, fluid sampling ability was lackingbecause samples were limited to two per trip and fluid identification could beknown only after the tool was retrieved at the surface. This not only hindersreal-time decisions but also can be costly, especially when dealing withmultiple pays and high daily rig cost, as in the deepwater environment. Toreduce costs, an advanced method of formation pressure and fluid testing had tobe used.
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