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
Authors: Liu Peiwu , Salem Abrar Mohamed , Pochetnyy Valentin , Alghannam Abdulrahman , Bosalhah Ammar , Almulla Sulaiman , Duggirala Vidya Sagar , Ayyavoo Mani Maran , Al-Bader Haifa , Al-Obaidi Abdulmohsen , Al-Saqabi Mishari , Mudhfer Khadejah , AlQenaei Abdulmohsen , Hadi Ahmed 
Published: October 2023

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.