Design and Implementation of Four Enhanced Recovery Projects in Bay Fields of South Louisiana

Abstract

Members SPE-AIME Abstract This paper reviews the design and implementation of four enhanced recovery projects that were initiated in the shallow-water environment of two bay fields located along the coastline of South Louisiana. These four projects are a caustic augmented waterflood, a miscible carbon dioxide waterflood, both in Quarantine Bay Field, and two polymer augmented waterfloods in the West Bay Field. The paper focuses on the design modifications required paper focuses on the design modifications required for the projects due to the hostile overwater environment and the logistics problems associated with the locations of the projects. Introduction In the last half of 1981, Gulf Oil Exploration and Production Company initiated four enhanced recovery projects in two bay fields, Quarantine Bay and West Bay, located in the environs of the Mississippi River delta in Plaquemines Parish, Louisiana. The location of the fields are shown on Figure 1. Landward, the fields are in the coastal marshes but both extend seaward some distance into open water. The average water depth in the bays is 2 1/4 m (7–8 ft). A wide range of enhanced recovery processes were considered by Gulf and three were chosen to determine their effectiveness in recovering additional oil from deep Miocene sands of the Gulf Coast. A caustic augmented waterflood, the QB 3 (RB) SU (Fig. 2), and a miscible carbon dioxide waterflood, the QB 4 (RC) SU (Fig. 3), were initiated in separate reservoirs in the Quarantine Bay Field. Two polymer augmented waterfloods, the WB 3A (RA) SU (Fig. 4), and the WB 3A (RB) SU (Fig. 5), were initiated in the West Bay Field. An existing water injection station was modified for polymer injection in the two West Bay projects; however, a new combination injection and projects; however, a new combination injection and production facility was built to accommodate the production facility was built to accommodate the Quarantine Bay projects. A total of eleven wells were drilled and fifteen were reworked to ensure adequate drainage and maximum areal sweep of chemical injectants in the four projects. PROJECT DESIGN PROJECT DESIGN Process Descriptions Process Descriptions Three different enhanced recovery processes were selected to evaluate their potential in improving oil recovery from reservoirs in the Miocene sands of the Louisiana Gulf Coast. The processes are caustic augmented waterflooding, miscible carbon dioxide waterflooding, and polymer augmented waterflooding. The results from these projects, in conjunction with results from previous y reported Gulf Coast enhanced recovery projects, will help Gulf determine which processes might be economically justified in large-scale enhanced recovery operations in Gulf Coast reservoirs. The Miocene sands are characterized by high permeability and porosity. The formation water permeability and porosity. The formation water salinity is high, being greater than 100 000 cm3/m3 (ppm) for each of the Gulf projects. The shallowest of the four projects is found at a depth of 2165 m (7100 ft) subsea and the reservoir temperature is 74 deg. C (165 deg. F). Only one of the four projects had previously been waterflooded, and that projects had previously been waterflooded, and that only on a limited basis. Current recoveries range from 23 to 43 percent of the original oil in place. The polymer augmented waterfloods are designed to be implemented in three phases:a preflush phase,a polyacrylamide polymer slug phase, phase,a polyacrylamide polymer slug phase, anda post polymer slug phase. The preflush will consist of a 30 percent total pore volume slug of treated and filtered bay water. The polymer slug will be a 30 percent total pore volume polymer slug will be a 30 percent total pore volume tapered slug. Its initial concentration will be 1200 cm3/m3 (ppm), reduced to 800 cm3/m (ppm) after injection of one third of the slug volume, then reduced to 400 cm3/m3 (ppm) for the final one third of the slug volume. The total volume of polymer scheduled for use in each project is 400 polymer scheduled for use in each project is 400 Mg (882,000 lb). The polymer will be prepared for injection by using treated bay water for the final dilution. The post-polymer slug phase will be a period of continuous bay water injection to drive the polymer slug through the reservoir. P. 341