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Abdelkarim, Islam (ADNOC Offshore) | Jadallah, Haitham (ADNOC Offshore) | Ness, Knut (ADNOC Offshore) | AL ALI, Salim (ADNOC Offshore) | Alzaabi, Mohamed (ADNOC Offshore) | Amer, Reem (BHGE) | Diaz, Nerwing (BHGE) | Gjertsen, Morten (BHGE)
Abstract After completing the drilling phase of the 8½″ section for a well in a giant mature field offshore Abu Dhabi, due to geomechanical challenges it was not possible to run the 7″ liner in a shale formation which was open for a long period of time due to rig repairs (top drive failure in open hole), exposing all reservoirs and compromising the field development strategy. After several unsuccessful attempts to run the liner and leaving a drilling BHA in the hole during one of the cleanout runs, it was decided to sidetrack around the fish to intersect the original 8½″ open hole section in order to recover the original hole and isolate the reservoir flow units from each other, which was critical for the field development since more than five reservoir layers were opened with water and oil bearings increasing the risk of damaging the reservoir integrity due to potential cross flow. Detailed measurement-while-drilling (MWD) survey analysis was conducted for the original hole in order to enhance surveys accuracy and minimize positional uncertainty. Typical survey management practices were implemented for Sag and Drilling String Interference; other techniques such as Dual Inclination, In-Field Referencing, and Multi Station Analysis were also applied. The implementation of these different survey management practices and their respective results are covered in detailed in the current article. Comprehensive planning was carried out, the sidetrack was accomplished and the original hole was successfully intersected at the first attempt. The advanced applied survey management techniques were crucial, particularly in the absence of magnetic ranging as the interval to intersect was open hole. The outcome of these corrections resulted in a shift of 8ft to the final well position, ensuring the correct direction and position for a successful attempt to intersect the well. This intersection was particularly challenging as the original hole had a 3D profile, thus it was critical to minimize both vertical and azimuthal uncertainties. Intersection was achieved with an RSS BHA, and the success of this intersection without magnetic ranging capability was only based on following a planned well trajectory that intersected the original hole surveys, clear validation of the accuracy of the surveys for both original and sidetrack holes. Achieving this challenging directional drilling goal allowed the completion of the well as per original plan, which was critical for the field development plan of these reservoirs. Based on the fact that there is very limited existing literature covering similar cases to the one presented, this current case represents a solid successful reference to be replicated in similar cases in the future covering these challenging applications of advanced survey management techniques.
Abstract This case history describes planning and execution of a deep relief well operation that resulted in re-entering, killing and abandoning a wellbore which was blowing in the subsurface. In 1994, a gas exploration well, Makarem, was sidetracked past a bottomhole assembly, which had become stuck almost 1,000m off bottom. A kick was subsequently taken, indicating charging of shallower horizons from a deep, sour, high-pressure gas reservoir at potentially high rates. Attempts to reenter the original wellbore while drilling ahead in the sidetrack hole were unsuccessful. The well was re-entered in 1997 with the objective of isolating the flowing zone to prevent potential environmental impact, future drilling problems, and the loss of hydrocarbon reserves resulting from uncontrolled flow of gas in the subsurface. This case history reviews planning and execution of a deep horning-in operation to locate and re-enter the 12 1/4" open hole below the bit of the stuck assembly, 3680m below surface. Key issues addressed during the planning phase included relief well strategy, positional uncertainty, well control scenarios, options for isolation and contingencies. An active electro-magnetic ranging technique was employed to successfully locate and track the target assembly to an eventual direct intersection with the crossflowing hole. Execution of the intersection plan is detailed, with emphasis on horning-in on the fish, borehole surveying techniques and quality assurance. Also covered is the operational organisation, and details of the activities following intersection, which included stabilisation, cleanout and abandonment of almost 1,000m of borehole which had been inaccessible for over 3 years. P. 367
Abstract The demand for indigenous supplies of natural gas in the UK and other countries in Europe has driven operations in the unconventional gas arena since the 1990s. In Coal Bed Methane (CBM) there have been attempts in the UK, Belgium, Germany, France and Poland. Dart Energy and its heritage company, Composite Energy, have been active in CBM in the UK since 2004, drilling 25 CBM wells in the UK, including 10 appraisal and development wells on the Airth field in central Scotland. A further 4 appraisal wells were drilled by the previous operator of the Airth field in the 1990s. The local Carboniferous coal geology, as with most European coals of Carboniferous age, is characterised by thin, numerous, low permeability, undulating coal seams. A number of different well designs were tried over the 14 Airth wells to meet the challenges of the local geology: initially vertical fracture stimulated wells; moving to geosteered multi-lateral horizontal wells, either intersecting a vertical well at the end of the horizontal section or as ‘updip’ branches off a motherbore without an intersection and finally multilateral geosteered horizontal wells intersecting a vertical well at the start of the horizontal section. The evolution in well design incorporated learnings from drilling operations, reservoir geology and production operations for each type of well architecture and advances in drilling technology in other CBM provinces around the world, adapting them to answer the particular subsurface problems encountered in the Airth field. Eventually, through this evolutionary learning process, Dart Energy was able to announce a commercial flowrate of 0.7MMscf/d from Airth 12 in January 2013, a multi-lateral horizontal well with a vertical well intersection at the start of the horizontal section. This paper describes the journey to that success, charting the evolution of CBM production well design on the Airth field, recognising the geological factors that drive well design, an evolution that can be applied to Carboniferous coal systems with thin, numerous and structurally complex coal seams found in other parts of the UK and Northern Europe.
The Gobe 4X sidetrack exploration well was drilled in a remote area of the Southern Highlands Province of Papua New Guinea using an innovative sidetrack technique for delineating hydrocarbons. After gas was encountered in the Gobe 4x straight hole, a non-conventional sidetrack was drilled down dip along the bedding plane of the reservoir sand and determined the gas-oil contact and the oil-water contact with a single wellbore thereby establishing the limits of the oil band. This was accomplished despite a difficult well trajectory, high deviation angle, large stepout and limited structural information.
INTRODUCTION AND SUMMARY
This paper is a case study of the Gobe 4X straight hole and 4X sidetrack exploration wells drilled in the Papuan Fold belt, an area of high current exploration and development activity. Located in the highlands of central Papua New Guinea (Figure 1), the Foldbelt is characterized by dense tropical jungle cover and rugged karst topography developed on the outcropping Miocene Darai Limestone. Usable seismic data is not obtainable and exploration is based on structural mapping using photogeologic and surface geologic data. Well targets are developed using objective horizon maps based on structural cross sections. Anticlinal hydrocarbon accumulations in the foldbelt typically have large gas caps; some have downdip oil rims.
In the past, conventional sidetracks and multiple delineation wells were required to determine the presence of an oil band and its updip and downdip limits. At Gobe 4X, a non-conventional sidetrack drilled downdip along reservoir bedding determined both the gas-oil and oil-water contacts. Thus, the oil band was delineated with a single wellbore, potentially saving the PPL-161 Joint Venture Participants the cost of two further wells to determine the updip and downdip limits of the oil band. The well was steered by frequently revising the structural model, target and well course. This was accomplished despite the difficult well trajectory, high deviation angle, large stepout, lack of seismic and limited structural information. The Gobe 4X sidetrack was drilled in 8-1/2 inch (in) hole and marks a break from the traditional sidetrack method of culling and recovering the 9-5/8 in casing, re-drilling 12-1/4 in hole, selling 9-5/8 in casing and drilling 8-1/2 in hole to total depth (TD).
The Gobe Trend is a 45 kilometer (km) long, sinuous anticlinal feature located southeast of the Kutubu Project, the site of PNG's first oil production (Figures 1 and 2). The Gobe reservoir is the 64 meter thick Iagifu Sandstone member of the Jurassic Imburu Formation, which occurs at depths of 6650 to 7300 feet (ft). Approximately 310 meters of Imburu Shale, the seal at Gobe, separate the Iagifu Sandstone from the overlying Toro Sandstone Formation of Late Jurassic-Early Cretaceous age (Figure 3). The Toro, approximately 67 meters thick, is overlain by up to 1200 meters of Ieru Formation shales and silts.
Dutta, Ashim (ADNOC ONSHORE) | Ahmed Al Hosani, Mariam (ADNOC ONSHORE) | Alejandro Aranda, Jose (ADNOC ONSHORE) | Masoud, Rashad (ADNOC ONSHORE) | Isiaka Jaiyeola, Abiodun (ADNOC ONSHORE) | Ahmed Baslaib, Mohamed (ADNOC ONSHORE) | Mohamed Al Bairaq, Ahmed (ADNOC ONSHORE) | Mohammed Al Hammadi, Adel (ADNOC ONSHORE) | Ahmad, Mubashir (ADNOC ONSHORE) | Radman, Velimir (ADNOC ONSHORE) | El Shahat, Ayman (ADNOC ONSHORE)
Abstract Recently multilaterals wells are drilled in selective reservoirs in ADNOC Onshore fields for development of hydrocarbon gas in Abu Dhabi. The targets are commonly thin multilayered carbonate reservoirs. The development strategy of multilaterals has significantly enhanced the reservoir contact aiding higher drainage. Multilateral wells can significantly reduce well counts while still achieving robust recoveries. Benefits of using multilaterals included the acceleration of gas production and the reduction in CAPEX/OPEX . The reservoirs are targeted by drilling duel and triple lateral holes. In triple lateral wells, a main horizontal borehole is drilled followed by laterals on either side of the main borehole. There are challenges of drilling multilaterals as the multilayered reservoir subunits are thin and selective drainage is planned in each sub layers in 6" horizontal sections. It is imperative to have a detail well planning with industry standard drilling technology to deliver successful multilaterals. During the well planning stage the laterals are planned in 60-80deg azimuthally apart from main both, on either side. The laterals drilled by performing open-hole sidetrack from the main bore, which apparently has a challenge of success. During initial stage of the campaign, lessons learnt from applied practices has encouraged an innovative way for successful multilateral drilling. Wells are landed on top of the target reservoir. 6" horizontal main bore hole is drilled with creating three humps in the initial part of the well trajectory. The humps are high inclination short section of well path with high Dog Leg Severity. These humps are strategically created at selected points with 300- 500 ft gap from each other and are used to kick off open-hole sidetrack of the lateral holes. Recorded real time inclination (RTI), Image log data and porosity of main bore along the humps are the key factors considered before executing the side track. MWD-LWD triple combo along with image log are used in the main bore and tools without radioactive source are used while drilling lateral holes to offset the risk of stuck-up of BHA carrying radioactive source tool. A detailed step wise operational procedure has been identified and introduced for the success of this development strategy. The high-confidence, successful open hole sidetracking strategy has aided maximum reservoir contact in 6" section with minimum risk and rig time and has substantially contributed to offset additional cost and rig time in all the multilateral wells in ongoing gas development drilling. This multilateral drilling and field development strategy has been a combined effort of geoscience and directional drilling and have paved way for successful open hole sidetrack campaign with proven standard procedures.