Arukhe, James Ohioma I (Saudi Aramco) | Al Dhufairi, Mubarak (Saudi Aramco) | Ghamdi, Saleh (Saudi Aramco) | Duthie, Laurie (Saudi Aramco) | Elsherif, Tamer Ahmed (Schlumberger Middle East SA.) | Ahmed, Danish (Schlumberger Middle East SA.)
Two new records exist in one of current world's largest oil increment field development projects in Saudi Arabia. The records set while achieving a well's intervention objectives include; 1. Attaining the deepest coiled tubing (CT) reach for rigless well intervention at 29,897 ft (9.11 km) measured depth in an extended reach open hole horizontal power injector well using a CT tractor and; 2. The first application of real time logging enabled through a wired motor head assembly via the tractor. The intervention objectives were to acid stimulate an open hole completed relatively deep in the reservoir with total depth of 29,897 feet and open hole length of 6,697 feet utilizing 2" CT with open hole tractor, to perform injectivity / falloff test, and to conduct real time logging for evaluating the reservoir's injectivity profile.
The paper examines several challenges that engineers and operators encountered during intervention in this well. A partially sealing high viscosity tar layer exists between the overlaying oil column and underlying aquifer. Operationally, the challenge was to overcome obstructions arising from tar accumulation during the well intervention. This challenge was overcome by the use of a solvent and the well was successfully acidized with the aid of the CT-tractor. The other concern was the tractor integrity while large amount of acid is pumped and the extended exposure time of tractor to acid. The tractor successfully handled huge amounts of corrosive fluids in a sour environment while providing the required pulling force to reach the total depth of the well to set the intervention record for tractor reach without adverse effects on the integrity of its O-rings, seals, and mechanical parts. In addition to organic deposits, azimuth changes in the well added to well entry challenges as a result of changes in hole inclination, doglegs, and azimuth. The application of real time informed decisions was critical in overcoming all the challenges, optimizing stimulation design, and yielding a notable and consistent injectivity increase with evidence of extended life and a true reflection of deep penetration into the damage zone. The successful re-entry will benefit industry operators confronting similar intervention challenges.
An extensive study of the field and its predominant drive mechanism revealed that production and simultaneous peripheral matrix water injection is the preferred depletion strategy. Extended reach wells and relatively complicated trajectories typically characterize the powered water injectors drilled for reservoir pressure maintenance. The injectors will support oil production from one of the largest field developments in the history of Saudi Aramco in the M field. The field development consists of 27 artificial islands linked by 41 kilometers of Causeway spanning the Arabian Gulf Sea. The blend of onshore, offshore, causeway and artificial island construction concept was the optimal field development option for the field because it results in only 30% offshore development and 70% onshore development. The chosen concept for the field development requires water injection wells to provide peripheral matrix water injection as pressure maintenance strategy to support oil production. A tar mat zone characterizes the field. About 65% of the powered water injection wells have lengths greater than 17,000 feet, beyond the normal reach of coiled tubing.
The world's first successful application of a wired motor head assembly to allow real time logging with a tractor in an extended reach open hole horizontal well has been recorded in Saudi Arabia. The well, located on one of two finger islands, was completed to a total depth of 29,897 ft. (9.11 km) MD; making it the deepest well with open-hole section in the field development, and outside of the reach of traditional tapered coiled tubing (CT) used for well intervention.
Using 2 inch tapered coil tubing and well tractor, the well was successfully acid-stimulated in 14 stages with a total of 3,850 barrels of (diesel) emulsified HCl acid recipe. This paper shows that although tractor interventions have a proven record and are the preferred deployment method for extended well stimulation, there still existed the uncertainty of conducting real time production logging while simultaneously tractoring. This additional challenge in the industry could be overcome by utilizing real time Electrical to Optical (EtO) production logging measurements simultaneously with the running of a tractor. A comparison of the pre- and post-stimulation injectivity indices on a separate run prior to the real time production log acquisition showed an eight fold injectivity index improvement from 53 bpd/psi to 400 bpd/psi. The resulting marked injectivity improvement from acid stimulation also showed the benefit of informed decisions from real time fiber-optic distributed temperature system (DTS) in fluid placement.
Practical applications of these outcomes include the acquisition of real time data of comparable quality with conventional e-line tools resulting in distinct technical and economic advantages in the development of the remaining parts of the field.
Others include the reduction in total well delivery costs from an ability to accurately evaluate well performanceand diagnose problems in real time. The ability to employ real time information to effectively stimulate extended reach wells provide assurance that stimulation can serve as a technical and an economic solution for addressing the relatively high skin damage problem post drilling and completion. Real time logging with the tractor is logistically efficient and allows real time acquisition of injection profiles with the possibility for improving data quality with return passes.
The well used to test real time logging with a tractor is one of several wells for peripheral water injection in the pressure maintenance strategy for the field development of one of the largest increments in Saudi Arabia's history. The field development is one of the company's commitments to meeting worldwide energy demand for the 21st century. The field is being developed with a combination of oil producer and powered water injector (PWI) wells. The PWI wells are typically open hole completed extended reach wells with more than 65% of the wells beyond 17,000 ft in length and outside the reach of coiled tubing. Figures 1a and 1b are cross section plots of the subject well. As most of the field is located in shallow waters the requirement of dredging offshore channels for drilling rig access was avoided with the construction of a causeway that straddles the field along the Arabian Gulf coastline. The causeway development entails the construction of a series of man-made islands from seabed sand and rocks. The primary artery of this causeway is about 21 km, with an additional 20 km of laterals or offshoots. The laterals form branches to 25 man-made islands designated for crude oil production and 2 finger islands designated for water injection. The two finger island PWI wells are for supplementing the injection pressure from wells in other injector drill sites along the flanks of the field's structure. Each of these islands holds about 10 well pads.
Safeguarding and restoring the normal ecosystems and environment of the Arabian Gulf in an active hydrocarbon province undergoing field development is a tough challenge. Nevertheless, a multidisciplinary team involved in this field development has maintained a profound commitment in stewarding natural resources of the major carbonate field in Saudi Arabia.
As part of the Kingdom's strategy to maintain crude oil production targets, production tests were needed to confirm potential of the wells in the Southern part of the field's structure prior to commissioning. The wells are located on drill sites in some artificial islands that were reclaimed from the sea. The six-well deliverability testing campaign should greatly enhance offshore field development, help to obtain reservoir characterization parameters, evaluate stimulation needs for producers, and assess comingling concept for selected wells. A total of 27 artificial Islands and a major transportation causeway were constructed by land reclamation from offshore waters of the Arabian Gulf. These facilitate onshore access to drill sites thus eliminating relatively more expensive fixed steel jacket rigs or platforms.
Due to land space limitation and well spacing constraints on the drill sites, a compact well test facility layout was specifically designed to achieve smokeless flaring, full combustion, and minimize environmental impact. The design consists of two heat exchangers, three-phase separators, i-loop systems for effective H2S scavenging and chemical mix with crude, surge tanks and air compressors. When deployed, this system helped to meet the test objectives and addressed space limitation challenges, mitigated risk to sea pollution in a sensitive marine environment, and forestalled uncontrolled release of hydrocarbons to the environment.
The completion of the cleanup and flow back operation on these wells with no single safety incident, uncontrolled release of hydrocarbons, or spill to nearby offshore waters was a major demonstration of leadership and a key contribution to well testing in similar environments.
Meeting global demands responsibly and reliably led to the company's development of the Y field close to the shoreline of the Arabian Gulf. Developing the prolific field is a crucial element in the company's energy supply strategy with a significant increment to the anticpated production levels within afew years. Due to the shallow water location, access to offshore drilling rigs would be impossible without extensively dredging offshore channels. The access challenge was handled by handled by building a causeway that connects to a series of artificial drilling islands. The primary causeway artery has +21 km total length with an additional +20 km of laterals. The laterals form branches of 25 islands designated for crude oil production. Two of the islands are dedicated for water injection to pressurize the field. The drilling islands and causeway were created from sand dredged from the seabed and protected with huge rocks around the slopes. Just as a serious commitment was in place for the causeway and bridge construction, a critically important environmental strategy was also developed to protect the delicate coast ecosystem during the field development. Apart from the sensitive marine environment, a relatively high H2S content in the crude, limited well spacing, and proximity to the public also contribute to the challenging nature of developing the field.
One of the current largest oil increments in the world in Saudi Arabia is undergoing field development. The southern part of the field traverses the Arabian Gulf Sea. The Production Engineering team crossed major hurdles in the development of this field with Causeways construction on artificial islands over drill sites to assess well sites.
Flowback options on wells in these drill sites to unload drilling fluids presented key challenges. The flowback objectives included well cleanup, stimulation, production logging, and extended well tests for reservoir characterization requirements. Flowback would also allow conducting electric submersible pumps (ESP) spin tests prior to ESPs installation.
A smokeless flaring option considered the heavy crude's characteristics with relatively high H2S content, possible emulsions from intermixing with completion fluids, interwell spacing limitations, and the sensitive nature of the nearby challenging marine environment. The choices were between using a conventional flare system and modifying the proposed layout to optimize the project's objectives while respecting the constraints imposed by a sensitive aquatic environment, highly sour crude, space limitations, and work conditions or implementing pre-existing conventional practices with the attendant risks of compromising health, safety, and environment.
The authors examine the processes leading to the implementation of a smokeless and an environmentally friendly flowback option. The discussion includes the modifications made to the burner system, and H2S removal from the gas and oil phases. Also a new methodology is presented that fully controlled oil and gas flow to the burner to mitigate the risk of burner flameout for the highest burning efficiency, minimizing spills, and enhancing safe operation. The authors examine the pros and cons of other welltest options such as to re-inject produced fluids into the same reservoir, different reservoirs, or injection into water injectors.
Key significant technical contributions include the presentation of several practical measures to avoid oil spills, and to guarantee ambient air quality. The welltest layout included several automation systems or the elimination of human interventionto deliver safely the project's objectives.
The drill sites sit on artificial islands constructed from piles of gravel and sand in about 22 feet of water. The Causeway concept itself was borne out of a need to protect the beds of sea-grass and algae in X bay, which supply abundant food for aquatic existence. The beds of sea-grass and algae are therefore the perfect home for species like shrimp, dolphins, crabs, fish, sea turtles, oysters, and some endangered classes. A prime objective was to sustainably manage the X field development while preserving this inherited fragile but untainted legacy of the environment. In addition to the sensitive marine habitat, proximity to public areas, limited well spacing, and a relatively high H2S amount in the crude all contribute to the challenging nature of this field development.