New Insight in Developing Tight Fractured Carbonate Reservoirs, Mishrif Formation, West Kuwait

Abstract

Abstract Mishrif is a tight naturally fractured carbonate oil reservoir in Minagish field of west Kuwait, developed over an asymmetrical anticline having wide variation in porosity ranging from 10% to 25% and a matrix permeability ranging from 0.1 mD to 4 mD. The reservoir is composed of multiple layers with a calcareous shale cap. It is exclusively being produced from the upper layers, with intensive focus being on a more porous M9 layer at 5,000 ft true vertical depth subsea (TVDSS). Given the limited permeability anisotropy (kv/kh) and lack of aquifer support, the drop in reservoir pressure can be severe. Even though there is large remaining reserves, the amount of oil actually participating in production could be limited. Most openhole producers are located in the north of the field where potential north/south and northeast/southwest faults associated with different types of fractures exist. In a successful development plan in Mishrif field 15 years ago, only a few wells were drilled. Then, the well behavior significantly changed for the 30 wells drilled to date in the Mishrif. This study proposes a new insight in developing Mishrif field arrived at through a detailed structural and geomechanical analysis to capture the variability of key reservoir properties and the affecting factors including well-to-well interference. Following the analysis, a new optimal stimulation workflow and new production practices were initiated to achieve effective and economical wells. In the northern part of the field, 23 producers are located mostly in regions with strong pressure depletion and significant well interference. Temperature logs run in problematic wells enabled identification of high-permeability zones and quantification of loss zones. The production surveys in high performing wells unlocked an understanding of the natural fracture characterization from image logs. These analyses were followed by chemical and mechanical isolation that has resulted in production improvement across many of the wells. The wells located in undeveloped central and southern regions have sustained flow capacity and higher reservoir pressure. This area shows a high remaining oil in place and historical well performance shows potential for sustained production. The current field development plan under primary depletion has been updated with drilling limited to undepleted regions to avoid the production interference via faults seen in the north of the field. The implementation of this detection and stimulation workflow presents a highly efficient and cost-effective solution for the stimulation of openhole tight carbonate reservoirs. The success of this intervention highlights the importance of continuously investigating changes in the drilling, completion, and stimulation approach to optimize production and maximize the recovery of resources from challenging reservoirs.