Optimizing Waterflooding EOR Through Cyclic Injection: A Case Study on the Hoople Field, Midland Basin, West Texas

Abstract

This paper presents a case study of implementation and results of cyclic injection EOR technique in Hoople field. It is located in Crosby and Lubbock Counties, west Texas and sits on the Eastern Shelf of the Midland Basin. The Hoople oil field, discovered in 1970's, is in its depletion stage with water cut greater than 95%. The reservoir rock consists of tidal flat dolomite and limestone interbedded with shale in Lower Permian Clear Fork Formation. Severe reservoir heterogeneity with low porosity and permeability are observed through core examination. This type of reservoir is suitable for cyclic injection. Cyclic injection consists of two stages for water injection: pressurization (or injection) and depressurization (injection shut-in). Cyclic injection was initiated in part of the Hoople field in 2020. We selected two sections in the field for pilot testing and completed a full cycle in each section. After encouraging results, the cyclic injection technique was deployed over the whole field. The large-scale operation consists dividing the field in four sectors to maximize water handling and optimize cyclic injection operations. Cyclic water injection has generated positive results. During depressurizing (or shut-in) half cycle, water production decreased dramatically with increasing oil-cut. Water production decreased 10% in each area while oil-cut improvement ranges from 13% to 33%. During the pressurizing (or injection) half cycle, oil production increases with total fluid production. The observed increase in total production ranges between 10% to 19%. The most significant finding is the consistent reservoir oil production and oil-cut response. Overall oil production has been kept at a stable level, countering the expected natural decline, suggesting that the cyclic injection led to enhanced oil recovery. Overall water production dropped significantly, reducing the cost associated with lifting from and injecting back to the reservoir. Cyclic injection has a very positive impact on the financial performance of the field development. The cyclic injection methodology, an alternative EOR technique, can be applied to other mature fields with similar reservoir properties.