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.

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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.

This paper discusses the outstanding performance achieved in a deep HPHT Jurassic formation drilled using Potassium Formate based fluid. This paper also describes methodology adopted for short term testing and stimulation of an exploratory well and finally the field results.Drilling and completion of deep Jurassic formations in the state of Kuwait is generally done with Oil Base Mud (OBM) weighted with Barite. During drilling, barite causes significant formation damage to the carbonates with natural fractures and it is essential to stimulate the well to evaluate the real reservoir potential. Formation damage is usually treated with matrix acid stimulation, however barite does not respond to acid. Kuwait Oil Company (KOC) was in search for an alternative drilling fluid causing relatively less formation damage and also responds to remedial actions. Potassium Formate brine with suitable weighting agent to achieve sufficient mud weight around 16ppg was selected for field trial in one of the exploratory wells. Formate based brine is a high-density Water Base Mud (WBM) which maintains rheological stability at high temperature and minimizes formation damage.Last 2,000 feet in 6" hole section of 18,000 feet well was drilled using 15.9 ppg Potassium Formate WBM. During short term testing, acid wash alone was sufficient to remove the formation damage and productivity has tripled which is unlikely in case of wells drilled with OBM.This case study shows how Potassium Formate based mud enhanced the productivity and reduced the testing time and cost. Based on the successful field test results, it is planned to drill future Jurassic deep formation with Potassium Formate based fluids in future.

Objective of this paper is to present our recent case-histories involving uncommon and unexpected Coiled Tubing (CT) intervention challenges in exploratory wells while testing and stimulating deep HPHT high Sour carbonate formations. Jurassic formations at around 17,000 feet in Kuwait are tested using cased-hole Drill Stem Testing (DST) system. 15K CT is employed during DST for displacement of kill fluids to achieve under balance prior to perforation, placement of acid for stimulation and for well killing operations. CT operational challenges encountered during testing deep exploratory wells are high pressure reservoir(>10,000 psi), limit on CT injection pressure>10,000 psi, pumping acid of 28% HCL, sour well fluid, salt plugging, etc. Well intervention under such challenging conditions requires proper planning, right equipment, techniques and procedures to ensure safe operation. Existing challenging conditions were well managed and objectives were met. A new problem of formation solids production after acidization of Kerogen rich carbonate/shale formation created a new challenge for CT operations which is unlike the common problem of sand production from the unconsolidated sand stone formation. In some wells, DST string got plugged with solids after acid stimulation and obstruction/stuck-up was encountered while operating CT. Another unexpected problem is the high H2S concentration of 35% in the recently discovered field. The unexpected challenges created unwarranted situation. It is a challenging task for operators to execute the safe and successful CT operations under these uncommon and unexpected conditions. Initially, even some of the service companies expressed their inability to operate CT under these extreme conditions. The unexpected problems are managed well within the available resources and the well test operations were executed safely and successfully. The new solids production operational experience has helped the operator to avoid the reoccurrence of CT stuck up thereby decrease the operational risk and increase the success rate. It has been proved practically in the field that CT can safely be utilized in high sour wells up to 35% H2S and increased the operator confidence. The experience gained, new challenges encountered, safe practices followed and way forward for execution of successful coiled tubing intervention in hostile environment will be discussed in this paper.