Jasem Al-Saeedi, Mohammed (Kuwait Oil Company) | Al Fayez, Fayez Abdulrahman (Kuwait Oil Company) | Rasheed Al Enezi, Dakhil (Kuwait Oil Company) | Al-Mudhaf, Mishary N. (Kuwait Oil Company) | Sounderrajan, Mahesh (Kuwait Oil Company) | Subash, Jaikumar (Kuwait Oil Company)
Drilling activities have increased in the State of Kuwait to enable the production of more gas from the Jurassic formations. The wells drilled to these prospects are challenging because of HPHT conditions, sour reservoir fluids and narrow drilling window.
Only vertical and deviated wells have been drilled to date, and in order to augment the production requirements horizontal wells were planned. For effective development of these reservoirs, horizontal well profiles were planned to increase the ability of the wells to access a permeable interconnected vertical fracture network which could result in high productivity and reserve recovery.
After detailed study, well SA-297 was selected as an appropriate candidate for a horizontal pilot project. In this pilot, the objective was to drill the first horizontal well through the Najmah reservoir in the North Kuwait fields. The project, being the first of its kind, posed many challenges. These included: drilling and casing 16?? hole at 60º well trajectory to 13,500 ft.; drilling the salt-anhydrite high pressure Gotnia at 60º inclination; drilling a slim pilot hole in the reservoir with K-formate WBM to facilitate positioning of the lateral; plug back this pilot hole and execution of a high DLS sidetrack just below 10 3/4" shoe; casing off formations with borehole stability concerns; drilling 6?? lateral hole by geo-steering; tubing plugging concerns during DST testing
Due to plugging of the tubing during testing, an intervention job was carried out with a workover rig to clear the tubing with coiled tubing in a live well and subsequently retrieve DST tools. This was a unique job carried out for the first time in Kuwait.
This paper will give details on the well construction, the complexities in the drilling operations and technical challenges faced while drilling the directional trajectory and in the special workover operations.
Acharya, Mihir Narayan (Kuwait Oil Company) | Kabir, Mir Md Rezaul (Kuwait Oil Company) | Al-Ajmi, Saad Abdulrahman Hassan (Kuwait Oil Company) | Pradhan, San Prasad (Kuwait Oil Company) | Dashti, Qasem M. (Kuwait Oil Company) | Al-anzi, Ealian H.D. (Kuwait Oil Company) | Chakravorty, Sandeep (Schlumberger)
The deep, sub-salt reservoir complex is tiered with fractured tight carbonate at bottom and top, with the two sub-units of "upper unconventional kerogen?? and "lower inter-bedded kerogen-carbonate?? in the middle. This depositional setting is challenging for horizontal well placement where the thicknesses of respective sub-units are about 50 and 30 feet with varying geomechanical and petrophysical properties. Additionally, this complexity poses limitations in completions and effective stimulation of the Kimmeridgian-Oxfordian reservoirs in several gas fields at development stage in Kuwait.
A horizontal well is placed in the lower sub-unit of the laminated complex of unconventional kerogen and fractured carbonate reservoir as a Maximum Reservoir Contact (MRC) type well. A pilot mother-bore was drilled and logged to identify the lithological properties across the entire vertical domain - facilitates the optimization of horizontal drain-hole placement within the targeted reservoir units.
No wellbore stability issues in drilling were predicted based on the geomechanical understanding where core-calibrated logs from offset vertical wells were considered. However, this modeling method did not have the functionality to integrate the impact of drawdown on the laminated formation which became unstable and collapsed during the short open-hole drill-stem test (DST) plugging the tubing prior to the final completions. An alternative "book-shelf?? geomechanical model was considered at pre-drill stage for predicting the wellbore stability. Once the drilling was completed, the time-lapsed multi-arm caliper indicated the validity of the alternative methodology in predicting the unstable stack of laminations in kerogen-rich strata.
The paper discusses an optimization methodology to enhance the understanding of static and dynamic geomechanical stability through the use of BHI data. Objective of the proposed method is to help improve the effectiveness of completions where wellbore stability due to geomechanical complexity in stacked-pay reservoirs is a primary wellbore challenge in deploying the completions and executing a subsequent stimulation and testing campaign.