A State-of-the-Art Water Shutoff System in Carbonate Reservoir: From Lab to Field

Abstract

Abstract Polymer gel systems have been utilized extensively as a water shutoff material to control and reduce excessive water production and eventually improve oil recovery. A novel water shutoff material with excellent gel strength and thermal stability has been developed to minimize water production zones based on various operational parameters such as pressure, temperature, pumping rate, treatment duration, and shut-in time. This paper presents the state of art polymer gel with an adsorption system from the laboratory phase to the thriving field implementation of water shutoff technology in carbonate formation. The developed polymer gel system comprises copolymer, organic crosslinker, and adsorption constituents. The water shutoff agent's gel strength and gelation time were deeply examined using high-pressure, high-temperature (HPHT) rheometers. The rheological properties, such as storage modulus (G’) and loss modulus (G") of matured gels with different compositions, were studied to identify the gel strength of each system. Additionally, the effect of temperature, polymer, and crosslinker on the gelation reaction was captured as part of the experimental research. Based on extensive lab experiments at downhole reservoir conditions, the water shutoff treatment was optimized to control water production from vertical oil well producers. The experimental results indicated that this water shutoff technology exhibited low initial viscosity for all systems below 20 cP at standard conditions, giving an advantage of pumping requirements during fluid mixing and injection to the targeted zones in the field execution. Once the water shutoff fluid travels downhole to the targeted zone, the temperature starts to buildup, and the gelation reaction begins. Consequently, the fluid viscosity is controlled at a specific bottomhole temperature based on liquid compositions, mainly polymer, crosslinker, and adsorption agents. This determines the gelation time between minutes to more than 10 hours. Therefore, this water shutoff gel can be placed smoothly into the target zone as a single-phase fluid with desired gelling time to plug the targeted formation. As for treatment design, the field testing utilized an E-coil string to run a production logging tool to spot the sources of water production and detect the bottomhole temperature and pressures essential to formulate the water shutoff system. The post-treatment flowback revealed promising results of this novel polymer gel system. The water shutoff fluid minimizes more than 60% of water production based on pre-treatment flowback. The newly developed water shutoff system is a promising polymer gel technology to control water production from carbonate oil formations. The experimental findings and field outcomes unveiled that this robust polymer gel efficiently plugged the water zone at high temperature and pressure conditions.