A Review of the Porter Field Unit Pressure Maintenance Project, Karnes County, Texas

Abstract

Abstract The Porter field unit is a 10 well project producing from a Pettus sand reservoir completely enclosed by faulting and sand pinch out. Primary reservoir performance was characterized by rapidly declining reservoir pressure and oil production, and increasing gas-oil ratios. A unit was formed in 1947. The program employed is injection of water down dip and return of produced gas to the gas cap. The project has been highly successful in arresting pressure and production declines and increasing ultimate recovery. Total oil recovery has already exceeded primary estimates by 29 per cent and productive capacity remains high. Movement of the water front has been uniform and water injection continued for four years before water production was obtained in the nearest producer 1,360 ft away. The success of the project is attributable to the willingness of the operators to conduct a long term project with high water injection pressures, and low injectivity, in order to obtain increased ultimate recovery. Introduction The purpose of presenting the history and performance of the Porter field unit is to show how success was achieved in spite of several adverse conditions. The reservoir rock is shaley, containing bentonitic clay. Water available for injection is comparatively fresh. Electric logs and core data show that permeability is variable throughout the field. At the start of water injection, abnormally high pressures were necessary to inject even a limited volume of water. A fair degree of success was obtained, however, and fortunately the second well to be used for this purpose proved to be very much better. Injection of gas has not as yet increased oil production directly. It has served however, to reduce reservoir voidage and hence helped to maintain reservoir pressure.