Abstract

A surfactant flooding system has been designed for application in a high salinity sandstone reservoir. The chemicals are mixed directly into produced brine, and are injected without the need of any reservoir preconditioning. Subsequently injected preconditioning. Subsequently injected polymer is displaced by produced brine. polymer is displaced by produced brine. A pilot project at the Manvel Field, Brazoria County, Texas, is being conducted in a watered-out fault segment. An isolated five-well pattern, two injectors and three producers, is used in conjunction with an producers, is used in conjunction with an active water drive. Injection and production rates were selected to maximize chemical utilization, and equalize the amount of chemical per unit reservoir volume in the various flow paths.

Results of both laboratory studies for process optimization and field tests for process optimization and field tests for reservoir definition, vital to pilot design, are presented. Descriptions of the chemical mixing facilities and chemical flooding schedules, including use of tracers, are covered.

Introduction

Many prolific water drive fields along the Gulf Coast contain significant amounts of residual oil after primary recovery. An enormous potential exists for enhancing this oil recovery with the use of surfactants. The reservoirs, however, contain high salinity water at relatively high temperatures, both of which adversely affect surfactant systems.

Previously reported chemical solutions, formulated for tertiary oil recovery, exhibit optimum properties at low concentrations of total dissolved solids, particularly low divalent cations. Application of these systems in higher salinity environments has required reservoir conditioning by preflush injection.

It is questionable that a reservoir can be adequately Preconditioned under the best circumstance, and it may be impossible to precondition a limestone or strong water drive precondition a limestone or strong water drive reservoir. Hence, it is highly desirable to develop a viable oil recovery process which can effectively displace tertiary oil in the existing reservoir environment. Such a process could have wide-spread applicability.

Laboratory testing, reservoir modeling and field testing programs were pursued for enhancing oil recovery under adverse reservoir conditions. This paper describes the design and field implementation of a test which employs surfactants mixed in produced brine and injected without preconditioning the reservoir.

Manvel Field, located in Brazoria County, 15 miles south of Houston, Texas, was selected as a representative reservoir to evaluate a surfactant/polymer process. Chemical injection was initiated in the Manvel Pilot in June 1977, with the equipment and field procedures reported herein. Oil production response has been obtained; however, it is too early to evaluate the process. process.

RESERVOIR DESCRIPTION

The Manvel Pilot project is being con ducted in the first Frio Sand named the Oligocene reservoir. This prolific reservoir produces with an active water drive and will yield about 60 percent of the original oil in place by primary recovery mechanisms.

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