With the scarcity of new field discoveries and depletion of existing mature fields, operators in Pakistan are keen on cost-effective rigless solutions to enhance production. In the northern region, one operator was looking to curb the water production of an oil well completed with a jet pump installation. The subhydrostatic nature of the well, naturally fractured reservoirs, and large producing units with multiphase reservoir fluids and active aquifers posed significant challenges for rigless well intervention for water control and zonal isolation. High water cut resulted in oil production loss and made the well uneconomic. An innovative zonal isolation method was required to overcome those challenges. The proposed solution comprised coiled tubing (CT) capable of acquiring real-time downhole measurements through fiber optic telemetry and delivering a through-tubing inflatable packer. The 2 1/8- in. packer was to be set in 4 1/2-in. liner with an expansion ratio of ~2:1. Planning and design considerations included selecting the bottomhole assembly (BHA) and performing pre-job quality checks of the inflatable packer and fiber optic cable. Downhole measurements verified accurate packer setting depth using a casing collar locator (CCL). To achieve adequate packer inflation without jeopardizing the packer integrity and to confirm proper anchoring of the packer onto the casing, downhole CT internal and annulus pressures were continuously monitored. During the first run, the liner tubulars were conditioned across the planned packer setting depth using a high-pressure rotary jetting nozzle. In the second run, the through-tubing inflatable packer was anchored, tested, and ultimately released at the target depth, providing a mechanical isolation above the water-invaded interval. Water shutoff is one of the most challenging remedial operations in the oil and gas industry. During the design stage for mechanical isolation, key steps such as proper wellbore conditioning, accurate placement technique, and effective sealing across the water-bearing zones must be carefully reviewed to increase the chance of success. Conventional CT solutions fall short when it comes to actual tool depth with errors as high as 0.3% being accepted as common. Likewise, critical factors for CT operations in subhydrostatic wells, such as precise control of fluid flow in pressure-sensitive tools and understanding of changing well conditions, are very difficult to validate through conventional CT. An advanced CT solution relying on real-time downhole data combined with a high-pressure rotary jetting nozzle and a through-tubing inflatable packer was able to deliver precise results, reducing the water production from 1,253 B/D to 93 B/D and increasing oil production from 48 B/D to 224 B/D. Furthermore, the production tubing remained in place, eliminating the need for a workover rig. Real-time downhole measurements also served as a safety net so the packer would not inflate prematurely, and to allow validation of downhole conditions throughout the intervention. By leveraging the use of real-time downhole measurements to accurately control the positioning and actuation of high-pressure jetting tools and through-tubing inflatable packers, critical interactions with the formation or the completion are achieved, improving operational reliability while reducing risk of failure for water shutoff operations in subhydrostatic wells with a narrow depth margin between intervals.

Environmental concerns and the economic aspects curtail usage of oil-based drilling fluids (OBDF) during the drilling operations through shale formations. The OBDF is highly effective in controlling the swelling potential of the clay-rich shale formations in oil/gas wells. Hydration of shale formation by water-based drilling fluids (WBDF) leads to several problems such as collapse of boreholes, tight holes and stuck pipe which may preclude further drilling and time loss in rectifying the problems, leading to heavy economic losses. Designing the drilling fluid that reduces the interaction with shale, is important for safe and efficient drilling. This study investigates the new gemini surfactants as shale swelling inhibitors in the field of drilling. To assess the performance of new cationic Gemini surfactants two reliable clay sources were considered. The first clay (Kaolinite) is from an unconventional formation and the second is sodium bentonite. The inhibition characteristics of gemini surfactants were tested using a dynamic swelling tester. Different formulations based on commercially available solutions for shale swelling inhibitors were applied and compared with cationic shale inhibitor. It was observed that the new gemini surfactants reduced the shale swelling by different percentages for various gemini surfactants based on their spacer length. It also showed acceptable performance compare with common shale inhibitors used in the industry.

Leak identification across well completions is a crucial operation in the oil and gas industry. A failure of well barriers can result in uncontrolled release of hydrocarbons and pose major risks to personnel and environment. Downhole gauges are widely used to provide pinpoint measurements of pressure and temperature across the completion; however, those measurements alone are insufficient to properly diagnose single or multiple well integrity issues. Alternative well intervention methods are needed to qualitatively estimate the location and number of potential leaks. For the past decade, distributed temperature sensing (DTS) has been used in wellbore completions and surface pipelines with preinstalled fiber optic lines to identify leaks by monitoring and processing temperature profiles across the length of the installation. The proposed methodology makes use of a similar principle, relying on coiled tubing (CT) to deploy the fiber optics and conduct DTS integrity assessment in wells completed without fiber optic lines. This use of fiber optics inside a CT pipe also provides simultaneous real-time downhole measurements, which include CT internal and annulus pressures, and casing collar locator (CCL), for precise depth control and accurate correlation of well parameters. In the south of Pakistan, the tubing-casing annulus pressure of a high-temperature gas well increased to near flowing wellhead pressure at the tubing, giving a clear indication that at least one of the completion components had failed, resulting in flow of hydrocarbons to the annulus. Yet, the high wellbore temperature limited conveyance of conventional logging tools to assess downhole completion integrity. A thorough analysis of well hydraulics was first conducted to gather the possible options to identify the leak using DTS. This enabled the determination of a workflow aiming to create enough differential pressure to generate particular temperature disturbance. CT equipped with fiber optics was run and stationed across the complete wellbore length, and DTS data were acquired for approximately twelve hours under changing well conditions, including shut-in and flowing periods. The acquired temperature information for each phase, along with pressure information, helped to narrow down the location of possible leak points. This methodology enabled the identification of a single, major leak point located at an expansion joint in the completion. The operator was able to riglessly set an annular plug to restore integrity, thus saving significant workover cost and time.

Exposure of production annulus with formation fluids due to tubing-casing communication is unfavorable scenario throughout well's life cycle. The communication paths are always susceptible to aggravate with the passage of time, eventually resulting in complete loss of well integrity due to failure of one of the integral well barriers and potentially causing major risk and hazards to environment and personnel. Accurate and most efficient actions are therefore required on war-foot basis to restore lost integrity. DST of an exploratory well in South Pakistan revealed the corrosiveness of reservoir fluid (26 % CO2), therefore, completed with chrome material. Well remained shut-in due to plant capacity constraints. Soon after well commissioning, pressurized annulus was reported. Initial investigation depicted hydrocarbons in annulus, however, Distributed Temperature Sensing (DTS) was later used to accurately locate the leak path. Conventional remedial options including tubing patch and work-over were ruled out due to extreme reservoir parameters and associated high cost as well as production curtailment. Placement of Resin-Based Isolation Plug (RBIP) in annulus was found to be the most feasible option to restore well integrity. Coiled tubing conveyed DTS was carried out in shut-in and flowing conditions that confirmed depth of leak path in completion string. Main reason of implementing this diagnostic technique was the unavailability of conventional logging tools compatible with high temperatures. DTS was run in conjunction with correlating tool (CCL) for precise depth determination with respect to completion jewelry. After exploring pros and cons of conventional remedial techniques, treatment through annulus was the only remedial option left to block the leakage path in completion string therefore, placement of RBIP on top of leak point was planned. This plug, once solidifies, restricts tubing movement due to thermal effects when exposed to production loads. Therefore, extensive stress analysis was essential to evaluate the integrity of anchored completion due to plug under various production loads throughout the well's lifecycle. With all possible risks critically assessed, RBIP along with bridging spacers was successfully poured in annulus during rig less operation. Well was kept in flowing conditions towards plant to avoid production curtailment throughout the operations. Currently, well is flowing, maintaining the necessary feed at plant and fulfilling country's gas demands with well integrity intact. Tubing-Casing communication and pressurized annulus has become common problem and plays significant role in maintaining the reputation and progress of E&P companies. Conventional methods are readily available to rectify such problems however, there are scenarios where wellbore conditions / parameters and economic feasibility may restrain their implementation. RBIP is a new technique in restoring well integrity through annulus and is successfully implemented for the first time not only in Pakistan Petroleum Limited (PPL) but in Pakistan.

The operation of bypassing the existing borehole by placing a kick off cement plug has historically been very well established and long-standing technique. Although placement of a cement plug appears to be a routine and relatively simple job, the instances of kick off plug not fulfilling the desired purpose are quite frequent requiring same degree of planning as primary cement jobs. Traditional cement slurry systems for sidetracking have been focused on the development of compressive strength by reduced water content. These cements exhibit low resistance to impact and toughness requiring multiple attempts to side track the well. An industry average for kick-off plugs is 2.4 attempts per kick-off, with 24 hours rig time associated with each attempt. This paper describes the engineered slurry system that incorporates unique properties of higher impact resistance, fracture toughness and load bearing capacity which resulted in slow ROP and sidetrack in 1 st attempt. The main conclusion will be supported by case study at the end of paper.

A major challenge in carbonate reservoirs is the highly-fractured nature of the rock. The flow rate may be high or low depending on the targeted fracture clusters. In addition, it is possible that flow rates vary from one region of the reservoir to another. Smart wells furnished with smart completion strategy presents great prospects to produce such reservoirs intelligently, thereby, helping to deal with heterogeneities rather smartly. It is established that early water break-through occurs when multi-lateral wells are completed with constant choke settings, and therefore one way to mitigate this problem is using smart completions that manage the unexpected production through fractures, thereby increasing ultimate recovery. The early water breakthrough is obvious because if a lateral section intersects a clusters of fracture zone, there is a possibility that these fractures may connect with the water zone that may trigger the breakthrough. This can be managed by preferentially regulating production from manifold laterals. The evident communication among the various laterals of the mother bore raises difficulty in optimizing the production from the variable productivity intervals. In theory, the optimization scheme of smart completion involves different constraints, nevertheless, the settings of the smart inflow control valve (ICV) is the single most important parameter that may prove to be the differentiating factor between a high producing well to a poorly producing one. This study engrosses its effort on the reservoir engineering characteristics of finding the optimum choke setting that would lead to maximum recovery. Computational Intelligence through Particle Swarm Optimization (PSO) is utilized as the integral algorithm to determine the optimal ICV configuration for a fishbone well in a naturally fractured carbonate reservoir. A commercial black oil simulator was used to determine the objective function; whose role here is to evaluate the fitness of a configuration of the choke; this was carried out under a workflow programmed in the MATLAB programming language that coupled the optimization algorithm with the numerical simulator. A single fishbone well, having 15 laterals was studied in order tot see the effect of the fracture network on the water breakthrough and consequent impact on recovery. Three different scenarios are developed to see the impact of optimization; a base case employing only multilateral well technology without the smart well completion, a smart well completion scheme with no optimization and finally the optimized smart well completion. The results very sequentially clarify the need for not only optimization but also highlights the role of intelligent completions for wells in the reservoir being studied. It is evident that without using smart wells, the water breakthrough is relatively earlier and produces less hydrocarbons, but as the use of smart wells is incorporated, the results start improving and for complete optimization scheme of the ICVs, it is observed that the recovery has increased by almost 80% from 21% to 38%. Moreover, the time to water breakthrough and eventually the cumulative water cut has also been managed quiet significantly.

The importance of improving the drilling performance in an E&P company cannot be under estimated as it directly impacts the overall cost of the project. The objective of drilling and well engineering management system is to address the technical and organizational aspects of Drilling operations and deliver the wells in safe and cost effective manner. The different tools that are the vital part of the Drilling and well engineering management system include gates review process for well delivery; section-wise after action review, lesson learned tracking system and non-productive time(NPT) tracking system for continuous improvement from the previous wells. Tools for knowledge and data management and analysis (including technical limits& field specific KPIs) and their input for the upcoming wells is also the part of the system. A cross deliberation, peer review process and auditing system is in place in the process for the compliance check. Notable impacts of the Drilling well engineering management system include rigorous well examination during the gates review process, enhanced risk assessments of various aspects of well planning. The system provides accurate and detailed monitoring of the drilling operations through various tools during the execution phase. Within one year of its implementation, the operator was able to improve the drilling performance by achieving huge benchmarks in exploratory and development prospects across the entire operated blocks. In some of the fields, where the drilling activity is progress for more than 50 years; the implementation of the management system provided around 100 to 150 % decrease in drilling time and cost in the benchmark wells. This paper includes the results from one of the major challenging fields; Adhi field in which subject changes were implemented successfully. This paper provides an overview of the management system, its implementation in the organization and outcomes and benefits achieved in the drilling efficiency through the system.

Over the past forty years, steering a horizontal well has evolved from geometric to structural to facies type and now productivity steering. This paper is aimed to summarize the evolution of wellbore steering and the impact of logging-while-drilling on well and reservoir performance. The quest for productivity drilling began in the late 1980s with the first generation of logging-whiledrilling (LWD) technology that provided directional and formation-evaluation measurements and basic data insurance in vertical and deviated wells. The primary applications were stratigraphic and structural correlation and rudimentary formation evaluation. A shift in LWD technology in the 1990s increased the focus on exploitation of smaller, tighter, and harder-to-reach reservoirs. This second phase saw the introduction of azimuthal measurements, borehole images, instrumented steerable motors, and forwardmodeling programs for well placement through geosteering. Well architectures became more challenging as well construction evolved from geometrical designs to wells steered by geological information. In the 21st century, geosteering entered its third phase; structural steering with deep-reading LWD resistivity measurements and high-resolution imaging. This allowed operators to reposition in real-time horizontal and high-angle wellbore trajectories in anticipation of structural changes ahead of the bit. Two recent developments since 2010 have taken geosteering to the next phase of productivity steering. The first one is reservoir mapping while drilling. It uses continuous bed boundary logs from deep azimuthal electromagnetic measurements. The second one is fluid mapping while drilling. It incorporates discrete/station measurements of reservoir rock and fluid properties from formation testing while drilling along with advanced mud gas logs. These developments have made it possible to estimate the productivity index (PI) of openhole section, in near real time, during reservoir drilling process. The productivity index while drilling estimate can therefore be used for drilling decisions as well as completion decisions and to evaluate the effect of trajectory undulations on well productivity while drilling. Real Time Productivity Steering (RTPS) is hence no longer a myth but a reality now.

This paper reviews the recently concluded first Near-Balanced Nitrified Stiff Foam application for a fractured low pressure reservoir formation; Sui Main Limestone in the Baluchistan region of Pakistan. The SML formation has presented extreme drilling challenges in this field. Severe loss circulation and reservoir influxes have made drilling this formation a night mare for the operator. Lot of Non Productive time has been spent while trying to pass through this formation. A recent application of the unconventional and innovative technologies has provided the client with an excellent solution. The major scope of work for this well is to pass the SML formation without having loss circulation and reservoir influx into the well bore while keeping good drilling performance and finally case the complete formation in one casing. A brief history of the Near-Balanced Drilling Technology using the Nitrified Stiff Foam fluid is provided in this paper which is followed by a discussion of the remarkable results achieved in this well. While performing the job the loss circulation problem was totally eliminated. Near-Balanced condition was constantly being monitored and maintained throughout the operation that resulted in no inflow from the reservoir into the well bore. Stiff Foam application also resulted in gaining outstanding drilling performance. All this resulted in the drilling of this formation in time less than half of the planned days. Finally the complete formation was cased within one casing without any complication. In Summary; application of the state-of-the-art and advanced technologies helped operator to eliminate the NPT associated with the drilling of this challenging formation. The operator was not only benefited with the rewards of this application but it also helped it to perform the Post Drilling operations in controlled, safe and desired manner. This paper reviews the process that was used to identify, plan, and implement these unconventional techniques. The purpose of this paper is to highlight all the benefits and lessons learnt while performing this first Nitrified Stiff Foam Near-Balanced Drilling mode application in Pakistan. This will help many operators in the designing and implementation of such techniques to challenging hydrocarbon bearing formations.

In certain onshore Pakistan wells, coiled tubing intervention has been used in plug-and-perf operations. Although the plug-and-perf technique is well described in the literature, the existing studies mainly cover fracturing and reservoir productivity aspects. This paper highlights coiled tubing operational techniques that are integral and vital to the success of coiled tubing plug-and-perf multistage fracturing. The application of coiled tubing plug-and-perf techniques to horizontal, high-temperature wells onshore Pakistan involved specific designs and new processes for the preparation, execution, and evaluation of the coiled tubing interventions. Planning and design considerations included the selection of the bottomhole assembly (BHA) in general and, in particular, the choice of logging head and upgrading the logging head operating envelope. During execution, efficiency was improved by reducing the number of coiled tubing runs with the use of addressable switches. The plug-and-perf sequence with coiled tubing was repeated successfully in multiple wells. The combination of the addressable switches used as part of the BHA to enable setting the bridge plug and perforating multiple sets of perforations separately in a single run was shown to be very successful. The use of the plug-and-perf with coiled tubing technique improved overall project economics by reducing operating time to half for each zone. These successes validate the advantage of deploying coiled tubing for multistage fracturing operations. Multiple operators have realized the value of this technique compared to other techniques commonly used in such operations.

Drilling techniques in exploration of oil and gas, adopted around the world, involves optimization of controllable variable during drilling operations. The drilling optimization procedures, involves better understanding of operational as well as equipment parameter on ROP (Rate of Penetration). The objective of optimization is to estimate a reasonable rate of penetration to reduce drilling time, cost and consequently early discovery of oil and gas. In this case study, optimum penetration rate of Kohat/Potohar region, where drilling is extremely problematic due to subsurface conditions specifically for muree and Kuldana formations, are obtained by two methods-mathematical & comparative. Comparative method uses cost per foot, specefic energy and rae of penetration with respect to depth comparison charts and give optimum drilling parameters while for mathematical model, BYM penetration model has been preferred to adress several drilling factors by using past drilling data of wells of Kohat region. Important parameters like ECD, Pore pressure gradient, evaluation of tooth wear and jet impact forces calculation are made for examining inter-relationship of controllable factors. At last a statistical approach of multiple regression analysis are made by using Matlab.Results of Matlab are further employed in determination of optimized parameters. Outcome from analysis are used to compare results with comparative approach and obtain optimum values of drilling rate, RPM and WOB for respective formations. Based on these approaches, potential risks can be mitigated which help to boost drilling performance and provides effective parameters for drilling of future wells in Kohat region.

This paper reviews the recently concluded first Weatherford Rotating Control Diverter application to a Loss and Kick scenario well in the Murree formation in Pakistan. The Murree formation in that area is considered as one of the toughest hurdle in reaching the target depths. The most common problems that are observed in this formation are loss and kick situations, which lead to conventional well control and then the hole tightening issues. In this well the client is having the same problems but in more adverse manner. There was a loss zone below and a gain zone above. They cemented the drilled portion of loss zone but whenever they try to drill further; got loss and then kick. Too much time was spent in controlling the well and then the well got tight and sometimes the string also got stuck. The major scope of work for this well with the use of Rotating Control Diverter is to divert the flow from the well, strip out of hole even during well flowing conditions and keeping surface back pressure whenever required. A brief history of the Flow Diversion Technique using Weatherford RCD is provided in this paper which is followed by a discussion of the benefits added by the RCD in minimizing the NPT associated with such drilling hazards. The RCD successfully diverted the gain/kick got after having complete or partial loss situations. The RCD helped to strip out of hole even having continuous well flowing conditions. In conventional techniques this is not possible to POOH without controlling the well. This saved time as well as saved the drill string from being got stuck or packed off. The squeezing jobs were also aided by the use of RCD as after pumping the pill; the string was pulled out without releasing the applied pressure. All these advantages lead to the completion of the well in a safe and efficient fashion. In Summary; applications of innovative and advanced technologies helped operator to perform the drilling operation fruitfully in this challenging formation in Pakistan. This paper reviews the process that was used to identify, plan, and implement this pioneering thought. The purpose of this paper is to highlight all the benefits and lessons learnt while applying this state of the art technology. This will help many in the industry to implement and design such innovative techniques and robust equipment for the mitigating drilling hazards.

The under balanced drilling technology has been under applied to the oil and gas well since the first cable tool well drilling. By the advent of rotary system the drilling fluid modified into mud system for controlled and smooth drilling operations. The under balanced technology revived again in mid-70’s due to the fore most need of such technology that can enable monitoring of reservoir fluid influx while drilling in progress and minimize reservoir damage. Some of the major prospect of under balanced drilling includes depleted zones, sub-normal zones and naturally fractured reservoirs. Where the prevailing myth about UBD Technology is its utilization in naturally fractured reservoirs, this paper will help to unfold enhance reservoir production achieved by UBD technology in conventional reservoirs. The purpose of this paper is to acknowledge the UBD Technology in conventional reservoirs, specifically. The prospects of application will be discussed with a major focus on mature reservoirs (reduced formation damage in depleted formations) and newly developed fields. Early Screening for the right reservoir and different screening criteria for the application of UBD technology in conventional reservoirs will help the readers to understand the limitations and applicability. The economic and technological advantages will be discussed along with value added by UBD technology in the form of increase reservoir production in normal pressure reservoirs which mostly get damaged to some extent with conventional drilling techniques. The paper will briefly describe the scope of UBD in Lower Indus and Middle Indus Basin. Through the work that has been done in similar reservoirs in Middle East, analogies will be developed. For further understanding, feasibility criteria of projects in local context will be considered that will enable the operators to take decision accordingly. The paper will also briefly explain the application of under balanced technology in normal pressure reservoirs with its limitations depending upon the UBD equipment safe pressure ratings in relation to reservoir pressures.

This paper covers successful Reaming with Casing job in Maino-17 located in Sindh, Pakistan. Throughout previous jobs during drilling in Miano block, Operator observed hole packoff and continuous caving, which raised concerns about running casing to TD. Specifically, drilling 12 ¼" hole section in Sui Main Limestone and Ghazij Shale, pressure and mechanical caving were observed throughout till TD. During wiper trip prior to run in hole 9–5/8" casing the hole condition was not good as it was packing off. Based on the challenges faced in Miano, Reaming with Casing technology was selected. The objective was to run and ream 9 5/8" casing to a total depth (TD) of 5,581 ft (1,701 m) in unstable hole conditions using Reaming with Casing. The difference in pressures between the limestone and the shale increased the possibility of hole caving during casing running. Operator’s team deployed the technology with internal catch tool to run and ream the casing through the pressurized formation. The Reaming with Casing technology provided remotely operated casing running, which eliminated the need for a stabber in the derrick, reduced the number of floor hands, integrated self-interlock system and reduced the risk of casing drop. While running in, the mud weight was 9.7ppg (1,162 kg/m3), which was kept to the minimum to avoid hydrostatic burden on loss prone formations, encountered an obstruction at 5,213 ft (1,589 m) and could not pass through. Using the Reaming with Casing, operator reamed the last ten joints of casing to casing shoe depth at 5,590 ft (1,701 m). The job was completed in approximately 12 hours without incurring any nonproductive time. Based on results, Reaming with Casing Technology was found very efficient, reducing approximately 50% of non-productive time, risk of POOH of whole casing string and associated cost as compare to conventional 9–5/8" casing job bedsides drill string/casing stuck in unstable hole. Using the Reaming with Casing technology enabled OMV to run the casing string to TD and improve operational efficiency in a challenging shale formation and enhanced safety by eliminating or removing personnel from the rig floor.

Geo-mechanics has always been a challenge during drilling process. It has also been a common observation that 40% of the over-all capex is given away during drilling process. Moreover, it also damages the land mass at large, loads of drill cuttings are generated from subsurface which are disposed on the earth surface, simply affecting the topography. Even, drilling does not prove to be successful in various cases as most of the exploratory wells are found to be dry this issue requires an ultimate solution. A well known technology called microhole drilling has been introduced to cope up with such concern. No doubt, all these specifications are achieved with the help of micro instrumentation. This study reflects the estimation of all the solids as wastes that are generated during the drilling process and imparts the environmental destruction. Microhole has been used effectively so far to hit the wells up to 700ft. Further, serious drilling issues are encountered but with the help of micro instrumentation it can be taken up to 5000ft or even farther. The main aspect that was found during the study that is microholes are drilled with the help of coiled tubing rig which consumes less disturbance area. In order to prove the metal of this technology a geo mechanical simulator is developed and model of microhole is even built on the developed software. The specifications and lithology of lower goru reservoir coordinates were used as input. Later, the results were compared to evaluate the recommended technology to avoid environmental issues and optimize the drilling program.

Over the last decade, new technologies and economic strategies have enabled operators to give new life to mature fields and old platforms. Production and economic optimization are main goals of reentry campaigns. With time, the industry has seen growing opportunities for reentry wells as mature fields and platforms are becoming older and less productive. Fully utilizing reentry technological capabilities and achieving successful operations require effective well planning and execution. Cutting and pulling of old completions and casings, wellbore cleanouts, plug and abandonment operations, section milling, mud systems, well integrity, cased-hole and open hole sidetracks, whip stocks, cutting/swarf handling, surveying tools, well collisions, and existing rig capabilities on platforms are the major challenges to the growth of reentry business. However, development of rotary steerable systems, logging while drilling, modern surveying tools, and under-reaming technologies have given impetus to the reentry well drilling market. From the concept phase of plug and abandonment to well delivery and production, seamless planning and communication is required among all the stakeholders. Modern surveying tools such as continuous north-seeking gyros and gyro while drilling have revolutionized the surveying industry in high magnetic interference environments, giving ease to planning sidetracks and accurate wellbore positioning in high well-density environments. Drilling close to the motherbores is becoming a common and attractive way of exploiting the reserves as no detailed logging and characterization is required. This has resulted in complexities of directional drilling and well collision risks. Risk of well collisions with producing wells is one of the biggest challenge in reentry wells.

Pakistan owns about 180 billion tons of coal buried under its surface. However, the share of the coal for power generation is just 2.25%, while oil has 58.5%. This conflicting policy of relying on imported and expensive oil is increasing budget deficit and disturbing the country economy. We studied different energy resources in detail and found that the coal deposits of Thar, approximate reserves of 175 billion tons can be an excellent energy source for the country to meet and fulfill the energy demand. This research shows detail analyses; chemical processes, reactions, and well linking techniques used for underground coal gasification. This study also demonstrates different operational problems and their solutions mainly water flux and weak strata along the coals seams. At block-V Thar Coal, one gasifier with 36 wells has been successfully completed and a test burn was carried. To link the wells for underground coal gasification, we investigated different techniques such as directional drilling, hydraulic fracturing, and reverse combustion linking. Thus we used reverse combustion linking because of its low cost and effectiveness to link the wells. So the syngas was successfully produced from the coal reserves of Thar by underground coal gasification. This produced low cost syngas after processing can be used for fertilizer industry, gas supply, power generation, diesel production, chemicals manufacturing, and in paint industry.

As the global HC exploitation paradigm shifts to the unconventional (low-quality) reservoirs; the deep uncertainty in their production processes involved makes the operators, following the Specific Discipline Approach, vulnerable to adopt the trial-and- error methods which can detriment the whole development plan and assimilate irreparable loss upon the foul decisions. Since each engineering discipline may have a piece of puzzle to find the best solution for achieving optimized production rates and economics, we can only hope to achieve the better results if we use a total system (reservoir to sales approach). Pakistan is facing the severe energy crisis, due to which the effective and sensible exploitation of the tight gas reserves has become inevitable. Integrated Asset Modelling (IAM) constructs a thorough way out by increasing communication and literally gets all disciplines "on the same page" by using a common model. The paper is based on designing a full field development plan of a tight gas reservoir (TGRs). It involves developing an integrated reservoir model and evaluating its performance for various reservoir and production scenarios, along with the economic analysis, to come up with an optimum gas field development plan. The methodology is carried out with two approaches (i) Integrated Tank Model (ii) Numerical 3D Model. The paper presents the usefulness of IAM and its systematic approach in production maintenance and optimization, crossfunctional collaboration and in effective field management of tight gas reservoirs. It will present detailed discussion on the economics, process cycle, modelling, optimization, game-changers and exploitation of TGRs along with case studies and intends to give valuable insight to the implementation of this integrated technique to the prevalent energy crisis of the country.

Mostly the wildcat wells are dry and extravagant, hence requires an ultimate solution during exploration. In order to overcome this issue, micro-hole drilling technology is highly result oriented technique these days. In this technique, the drilling holes with diameter ranges between 1.36" to 2.00" inches achieve the depth of 700ft using coiled tubing, drilling rig unit and micro-hole instruments. This paper covers the definitive elucidation to make the whole process leaving less environmental foot prints and hit the depth upto 5000ft economically. This could be achieved by introducing micro sized casings by means of micro instrumentation and coiled tubing unit along with the provision of low cost, exploratory wells in reducing material, intensive labor and supporting equipments. An integrated digital model of well bore has been developed using drilling calculator using the parameters of Sindh province lithology. The results were analyzed to investigate the influence of this technology, by comparing cost and depth graphs. It is elucidated that this technique is more environmental friendly and promising in terms of minimum cost of exploration.

Drilling horizontal wells is a standard practice in the oil industry. Placing hydraulic fractures along the horizontal section of the well, to increase hydrocarbon production, is also rapidly gaining popularity, especially as more tight formations, even shale, are targeted. Understanding the behaviour of each individual fracture requires production logging. This results in additional cost and also puts the well under "operational risks". It is desirable to use pressure data to understand the well behaviour, as this is readily available due to modern completions usually having permanent pressure gauges installed. Also, pressure data can be obtained without putting well at any "operational risks". In the region around fractured horizontal well, multiple flow regimes occur simultaneously. In pressure transient data usually a combination of all the flow regimes is observed making characterisation of the reservoir difficult. In this paper, a comparison of the existing analytical approaches is made to analyse pressure transient data for a horizontal well intercepted by multiple fractures. Using the analytical solutions of the diffusivity equation presented by different authors for a multiply fractured horizontal well, the dimensions of Stimulated Reservoir Volume (SRV) are calculated. Also, the number of active fractures and the flow rate from each fracture are determined using the pressure data. The time for the start of interference is calculated and the time dependence of individual fracture flow rates is also estimated. An observation about the inability to find the orientation of fractures is also made.