Advanced Technology Improves Recovery at Fairway
Authors: Lackland S.D. , Hurford G.T. 
Published: December 2007

The most important decision made in the early stages of this miscible recovery project was to hang loose. The original plan of operation allowed for injecting all gas, all water, or any combination, depending upon what new information was gained as the project went along. Radioactive tracers, new logging techniques, numeric modeling, and sophisticated down-hole equipment provided that information.

Introduction

The Fairway (James Lime) field is about 30 miles south of Tyler, Tex. The discovery well was drilled in July, 1960. near the eastern edge of the field, which eventually proved up over 400 million bbl of oil in place under about 23,000 acres. The 10,000-ft James Lime reservoir is a reef development at Fairway, quite different from the regional character of the formation. Three major zones exist in the reservoir as a result of differing conditions of reef growth environment. From the start, this complex, highly stratified, variable-permeability, reservoir offered quite a challenge to the operators. The James Lime oil is an undersaturated 48 degrees API-gravity crude containing from 1,350 to 1,600 cu ft of solution gas per barrel. Saturation pressure varied with depth and ranged from 3,950 to 4,350 psia. The reservoir fluid was determined to be miscible, with lean hydrocarbon gas or flue gas at about 4,800 psia - about 400 psi below the initial reservoir pressure. Connate water saturation ranged from 10 to 30 percent, and the porosity averaged about 12.5 percent. Unitization studies showed that incremental economics favored an alternate gas-water high-pressure miscible recovery project over waterflooding or immiscible gas injection. The operators recognized that many miscible projects had experienced poor recovery and even lost projects had experienced poor recovery and even lost money. Alternating gas and water injection represented the "outer limits" of miscible recovery technology available at the time and involved a high degree of risk. The decision was made to go ahead with the alternating approach, but with a program designed to have a large degree of operational flexibility. In this manner, necessary changes and adjustments could be made along the way. Additional recovery from the alternating gas-water high-pressure miscible recovery technique in use at Fairway is significant. Production exceeded the estimated primary reserves of 65 million STB of oil in June, 1971 (see Fig. 1). Currently the Unit is producing the top allowable of 40,500 BOPD. producing the top allowable of 40,500 BOPD. Injection capacity determines the maximum production rate at Fairway. The average reservoir production rate at Fairway. The average reservoir pressure has been maintained essentially constant at pressure has been maintained essentially constant at 4,500 psi since early 1970. An expansion program to increase gas injection capacity from 70 to 100 MMcf/D and water injection from 60,000 to 90,000 BWPD is currently in progress. With the increased injection capabilities and 13 new wells, now drilling. the Unit will be capable of producing at 100-percent market demand factor, about 53,000 BOPD for about 2 years before it declines as a result of an increasing voidage of injected fluids.

Mobility Control

The use of water injection to restrict the mobility of the injected gas is the key factor in the improved recovery of the Fairway project. A reduction of viscous fingering of the gas and improved sweep efficiency through water injection is very important in the over-all control of the Fairway project. Many of the early indications of fingering were in the north end of the field (Fig. 2) where gas injection was concentrated initially. Fig. 3 illustrates the typical relationship between producing trends and injection cycles. producing trends and injection cycles.

JPT

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