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This article, written by Editorial Manager Adam Wilson, contains highlights of paper SPE 147247, ’Successful Discovery of Light Oil From an Unsuccessful Paleozoic Well Through Re-Entry - A Case Study of an HP/HT Well,’ by Haifa Al-Bader, SPE, Yousef Zaid Al-Salali, SPE, Vidya Sagar Duggirala, SPE, A. Manimaran, and S. Packirisamy, SPE, KOC, prepared for the SPE Annual Technical Conference and Exhibition, Denver, 30 October-2 November 2011. The paper has not been peer reviewed. An exploratory well, the second deepest in Kuwait, had been drilled in the Mutriba field to 22,094 ft. Two formations, Kra-Almaru and Khuff, were perforated and tested. The tests revealed the presence of sparse gas, and it was decided to test and complete this well in the Jurassic formation through re-entry. The re-entry in this ultradeep well was full of challenges; however, by overcoming all the challenges, this well was successfully perforated, stimulated, and tested, which led to the first commercial discovery of oil and gas within the Jurassic reservoir in the Mutriba field. Introduction Two zones in Paleozoic and Triassic sections were perforated and tested separately to evaluate the presence of hydrocarbon between 18,500 and 21,500 ft. The well was completed in 2004. After undesirable results were obtained from the Triassic and Paleozoic formations, exploration teams studied the feasibility of testing Jurassic formations in this well through re-entry. Testing Jurassic formations in the Mutriba field from an existing well will be more economical than drilling a new well. A snubbing unit was deployed in 2008. In 2009, a suitable workover rig was deployed to test Jurassic formations in this previously drilled well. The location of the Mutriba field is shown in Fig. 1. A snubbing unit had been used to isolate the open perforations of the Triassic zone with cement. Subsequently, a workover rig was deployed to test the prospect of a Jurassic reservoir. Testing the Jurassic reservoir behind two heavy-walled casings (7 in. 46.4 lbm/ft and 8⅝ in. 40 lbm/ft) combined with extreme sour and high-pressure/high-temperature (HP/HT) conditions warranted high health, safety, environment, and technical precautions. Challenges for re-entry to this well included HP/HT conditions, a high surface pressure, and well-killing issues. Testing of the formation fluid revealed the presence of an unexpectedly high concentration of H2S (20%) and CO2 (2%), which presented challenges for coiled-tubing (CT) operations, stimulation, flowing the well, and fluid disposal.
- Asia > Middle East > Kuwait > Northwest Kuwait (0.87)
- Asia > Middle East > Israel > Haifa District > Haifa (0.25)
Deep Workover Challenges of an HP/HT Sour Gas Well - Case History of Mutriba 12
Jasem Al-Saeedi, Mohammed (Kuwait Oil Company) | Al Fayez, Fayez Abdulrahman (Kuwait Oil Company) | Rasheed Al Enezi, Dakhil (Kuwait Oil Company) | sounderrajan, mahesh (Kuwait Oil Company) | Al-Mudhaf, Mishary Najeeb (KOC) | Mckinnell, David Charles (Total)
Abstract Mutriba 12 is a deep 20,000 psi exploration well originally drilled to search for non-associated gas in the Triassic/Permian formations. During final testing operations the tubing became plugged with salt deposits and the well was suspended. The decision was taken to permanently abandon the lower zones and examine the possibilities of using the well to explore the hydrocarbon potential of the upper Jurassic horizons. The main re-entry objectives were to clean out the salt from the tubing string, permanently abandon the lower gas zone, cut and recover the tubing, perforate through multiple casing strings and safely test the upper formations. To meet these objectives the operations were planned in two parts with a Heavy Duty HP/HT Snubbing Unit used for tubing clean out / gas zone abandonment followed by a Deep Workover Rig to remove the tubing string, prepare the well and conduct the testing. Extensive planning and preparation were necessary involving detailed evaluation of all possible scenarios for key operations. During operations, significant challenges were encountered which dictated the employment of innovative methodologies and practices. These included confirming the top of abandon plug of 20K well test zone inside the tubing, working with high mud weights and restricted geometries, coiled tubing use under high pumping pressures, cutting / recovery of the tubing filled with solid laden heavy mud, adaptation and deployment of special tubing cutting mechanisms, perforation through multiple casings, and extended well testing in highly corrosive environment with fluids containing up to 24% H2S and 40% CO2. This paper will present a case history of the well, mainly concentrating on the operations with the workover rig, and including details on planning and contingencies, job design options, special equipment items, program development and operations along with conclusions and lessons learned. Introduction Mutriba-12 (MU-12) is a deep vertical exploration well originally drilled to investigate the hydrocarbon potential of the Triassic/Permian formations. The well was drilled and cased to a depth of 22,094 ft. and production testing was carried out to evaluate the Khuff and Sudair formations. In the course of testing these zones, complications occurred where saline water was produced along with gas, and salt deposits were formed which eventually plugged the tubing string. The operations were suspended at this time and following a review of the well situation it was subsequently decided to re-enter the well to permanently abandon these lower zones. The objectives of the first workover were to clean out the salt from the tubing string and permanently abandon the lower gas zone. At the time of the intervention the well was exhibiting high surface pressures, and a Heavy Duty Snubbing Unit was used to clean out the salt bridges and kill the well with an 18.9 ppg Oil Based Mud. A cement plug was then placed above the perforations, from production packer bore to up inside the tubing string in order to isolate the lower tested interval. As there was 19.8 ppg mud in the casing / tubing annulus above the packer, the Snubbing Unit work string was run in to tag the top of cement and to increase the mud weight inside the tubing string to 19.8 ppg. No firm cement top could be located with the Snubbing Unit string and high pressures were recorded while attempting to displace the tubing contents, therefore the well was left with 18.9 ppg mud in the tubing.
- Asia > Middle East (0.69)
- North America > United States > Texas (0.28)
- Asia > Middle East > Kuwait > Jahra Governorate > Arabian Basin > Widyan Basin > North Kuwait Jurassic (NKJ) Fields > Marrat Formation > Upper Marrat Formation (0.98)
- Asia > Middle East > Kuwait > Jahra Governorate > Arabian Basin > Widyan Basin > North Kuwait Jurassic (NKJ) Fields > Marrat Formation > Sargelu Formation (0.98)
- Asia > Middle East > Qatar > Block 4 > Khuff Field > Khuff Formation (0.94)
Challenges in Testing and Completion of Highly Sour HPHT Reservoir in the State of Kuwait
Al-Salali, Yousef Zaid (Kuwait Oil Company) | Al-Bader, Haifa (Kuwait Oil Company) | Duggirala, Vidya Sagar (Kuwait Oil Company) | Ayyavoo, ManiMaran (Kuwait Oil Company) | Subban, Packirisamy (Kuwait Oil Company) | Al-Ibrahim, Abdullah Reda (Kuwait Oil Company) | Rajkhowa, Anupam (Kuwait Oil Company)
Abstract Testing and completing deep reservoir in the state of Kuwait is challenging due to high contrast in formation pressure over the 4,000 feet section (13,500 ft to 17,500 ft). Recently, a new structure located in the North-Western part of Kuwait area was drilled and tested with deep drilling rig. Formations in this deep structure have very low porosity and permeability with naturally fractured reservoir. During short term testing, wells produced oil and gas with unexpectedly very high H2S(20%-35%), the highest H2S content in any reservoir so far discovered in the state of Kuwait. Since the reservoir was rated as HPHT and sour, it was a challenging experience to test all the wells safely and successfully. Unfavorable conditions such as high pressure, high temperature, high H2S and CO2 content require special equipment, tools and treatment to test and complete exploratory wells. The targeted formations were perforated using deep penetration Tubing Conveyed Perforating (TCP) guns, stimulated with emulsified/retarded acid, tested with Drill Stem Testing (DST) tools and sampling was done. Meticulous planning and testing strategies could overcome all challenges and high sour reservoir was successfully tested safely without any incident. The wells were flowed only for short period due to high sour nature of the reservoir fluid and safety reasons. However, data collected during short term testing helped in understanding production capability, fluid and reservoir characteristics which is vital for delineation/development of the new field. Methods developed, data obtained and expertise gained in testing and completing high sour wells will be useful for the future development of sour gas reservoir. Aim of this paper is to describe the actual challenges encountered and lessons learned during testing and completion of hostile environment wells. This paper also aim to present techniques and approach adopted to address the operational risk and HSE issues during perforation, Coiled Tubing, stimulation, well testing and sampling operations. Introduction Exploration of deep reservoirs has become very important to produce high pressure gas and light-oil to meet the country's gas requirement. Jurassic carbonate reservoirs in Kuwait fields are deep, low permeable, High Pressure High Temperature (HPHT) and generally contain sour volatile oil/condensate and gas. Formations of these deep reservoirs are tight and naturally fractured carbonate reservoirs. Najmah(NJ), Sargelu(SR), Upper Marrat, Middle Marrat and Lower Marrat are the five formations proved as a hydrocarbon bearing reservoirs. Najmah/Sargelu formations are tighter than Marrat formations. Najmah Formation consists of Limestone at the top part and Shale to the bottom. Sargelu Formation consists mainly of shale and limestone. Najmah & Sargelu (NJ-SR) are naturally fractured reservoirs. So, fractures play an important role in production from NJ-SR formation. Marrat Formation consists mainly of limestone, occasionally with streaks of anhydrite at the top and with streaks of shale at the bottom of this formation. The core analysis of Middle Marrat formation shows that dolomitization plays major role for matrix porosity enhancement which is responsible for good reservoir character.
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (0.65)
- Geology > Rock Type > Sedimentary Rock > Carbonate Rock > Limestone (0.65)
Abstract Testing and completing deep reservoir in the state of Kuwait is challenging due to high contrast in formation pressure over the 4,000 feet section (13,500’ to 17,500’). Recently, a new structure located in the North-Western part of Kuwait area was drilled and tested with deep drilling rig. Formations in this deep structure have very low porosity and permeability with naturally fractured reservoir. During short term testing, wells produced oil and gas with unexpectedly very high H2S(20%–35%), the highest H2S content in any reservoir so far discovered in the state of Kuwait. Since the reservoir was rated as HPHT and sour, it was a challenging experience to test all the wells safely and successfully. Unfavorable conditions such as high pressure, high temperature, high H2S and CO2 content require special equipment, tools and treatment to test and complete exploratory wells. The targeted formations were perforated using deep penetration TCP guns, stimulated with emulsified/retarded acid, tested with Drill Stem Testing(DST) tools and sampling was done. Meticulous planning and testing strategies could overcome all challenges and high sour reservoir was successfully tested safely without any incident. The wells were flowed only for short period due to high sour nature of the reservoir fluid and safety reasons. However, data collected during short term testing helped in understanding production capability, fluid and reservoir characteristics which is vital for delineation/development of the new field. Methods developed, data obtained and expertise gained in testing and completing high sour wells will be useful for the future development of sour gas reservoir. Aim of this paper is to describe the actual challenges encountered and lessons learned during testing and completion of hostile environment wells. This paper also aim to present techniques and approach adopted to address the operational risk and HSE issues during perforation, Coiled Tubing, stimulation, well testing and sampling operations.
First Successful Openhole Multistage Completion and Acid Fracturing Treatment to Unlock the Production Potential in an HP/HT, High-H2S Exploratory Well in North Kuwait
Liu, Peiwu (Reservoir Performance, SLB, Kuwait) | Salem, Abrar Mohamed (Reservoir Performance, SLB, Kuwait) | Pochetnyy, Valentin (Reservoir Performance, SLB, Kuwait) | Alghannam, Abdulrahman (Reservoir Performance, SLB, Kuwait) | Bosalhah, Ammar (Exploration and Well Surveillance, Kuwait Oil Company, Kuwait) | Almulla, Sulaiman (Exploration and Well Surveillance, Kuwait Oil Company, Kuwait) | Duggirala, Vidya Sagar (Exploration and Well Surveillance, Kuwait Oil Company, Kuwait) | Ayyavoo, Mani Maran (Exploration and Well Surveillance, Kuwait Oil Company, Kuwait) | Al-Bader, Haifa (Exploration and Well Surveillance, Kuwait Oil Company, Kuwait) | Al-Obaidi, Abdulmohsen (Exploration and Well Surveillance, Kuwait Oil Company, Kuwait) | Al-Saqabi, Mishari (Exploration and Well Surveillance, Kuwait Oil Company, Kuwait) | Mudhfer, Khadejah (Exploration and Well Surveillance, Kuwait Oil Company, Kuwait) | AlQenaei, Abdulmohsen (Exploration and Well Surveillance, Kuwait Oil Company, Kuwait) | Hadi, Ahmed (Packers Plus Energy Service, Kuwait)
Abstract In the north of Kuwait, developing a deep high-pressure/high-temperature (HP/HT) exploratory reservoir is challenging due to high H2S and CO2 concentration in the reservoir fluid. The studied field is located in North Kuwait, and the first well that showed commercial potential was in the middle Marrat reservoir. This paper presents a case study of the first well in this field where an openhole multistage completion was successfully installed and acid fracturing treatment was applied, achieving significant results. The well was successfully tested, which ascertains promising production potential in this area. The subject well is located in a strategic field in the north of Kuwait and it was targeting Middle Marrat formation to evaluate the reservoir production potential. It is a high angle deviated well (maximum inclination 57°) drilled to 19,000 ft (about 5.79 km) measured depth and close to the bottom of the Middle Marrat formation. Hydrocarbon shows were observed while drilling in the Middle Marrat interval, which prompted a completion and production test. The well was completed with a 15,000-psi openhole multistage completion system including closable fracturing ports with corrosion-resistant alloy tubing. The shallowest closable fracturing port was opened accidentally and was successfully closed after multiple well intervention operations, and acid fracturing treatments were effectively carried out to all three stages individually. After acid fracturing treatment, high H2S and CO2 concentration of 31% and 38% respectively, were detected in the flowback fluid. The well testing was intermittent due to unfavorable wind conditions, safety concerns, and limitation of the surface testing equipment. The H2S scavenger fluid was dosed to protect the surface testing equipment and lines during cleanup and during the flow period. The well was successfully tested, and short-term stable oil production shows higher than 3,000 B/D, which is much higher (by more than three times) than the offset vertical exploration well in the same field. However, a prolonged flow period and rate measurements could not be achieved due to equipment limitations in high sour gas conditions. A feasibility study is being conducted to perform long-term production testing with special equipment. This paper describes the main operation and technical challenges encountered in this well. The well intervention operation and lessons learnt are also highlighted along with the first openhole multistage completion technology used in this field. The success of the three-stage acid fracturing treatment and well testing with high H2S environment of an exploration well delivered breakthrough results, and it provides a production benchmark to develop the Middle Marrat reservoir in the exploratory fields in North Kuwait. Moreover, a flow test result of a vertical offset well in same field which was stimulated with matrix acidizing only is given to show a good comparison in flowback result and well productivity between the two different cases.
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock (0.68)
- Geology > Sedimentary Geology > Depositional Environment > Transitional Environment > Tidal Flat Environment (0.46)
- Asia > Middle East > Kuwait > Northwest Kuwait > Arabian Basin > Widyan Basin > Mutriba Field > Gotnia Formation (0.99)
- Asia > Middle East > Kuwait > Jahra Governorate > Arabian Basin > Widyan Basin > North Kuwait Jurassic (NKJ) Fields > Marrat Formation > Upper Marrat Formation (0.97)
- Asia > Middle East > Kuwait > Jahra Governorate > Arabian Basin > Widyan Basin > North Kuwait Jurassic (NKJ) Fields > Marrat Formation > Sargelu Formation (0.97)