Abstract

This study is an investigation of the higher pressure gas reservoirs, often referred to as "geopressured" gas reservoirs due to the apparent support of the earth's overburden by the reservoir fluids. The geographical area investigated for geopressured reservoirs is limited to the onshore and offshore area of Southwestern Louisiana. Within this area, most of the gas producing reservoirs are Miocene age; however, older reservoirs (to Eocene age) are also found.

The contribution of this study is to call attention to the occurrence of geopressured reserves and the favorable economics of drilling developing and producing these reserves. The unexpected distribution of the larger percentage of economical reserves at the higher pressure gradients reverses the previous concepts that geopressured reservoirs would contain small volumes of reserves. This is of particular significance to the domestic industry which must continue to drill deeper to replenish its reserve storehouse.

Introduction

The correlation of the ratio or gradient of reservoir pressure to reservoir depth expressed at the geostatic ratio and the volume of recoverable reserves from above normally-pressured gas reservoirs is the objective of this study.

The geostatic ratios studied were above normal, meaning the reservoir pressure encountered exceeded the pressure exerted by a column of sea water at the depth the reservoir was penetrated. Reservoirs that contain penetrated. Reservoirs that contain higher-than-normal pressures are considered to be supporting a portion of the earth's overburden. They are often called "geopressured reservoirs," broadly meaning "earth pressured."

Geopressured reservoirs probably were first encountered by drilling wells over thirty years ago. Early well penetrations in these reservoirs could not be controlled and the wells were abandoned. The first such occurrences would likely have occurred along the Louisiana-Texas border of the Gulf of Mexico; however, geopressured reservoirs have been discovered in several foreign countries. Data from geopressured gas reservoirs located in South-western Louisiana (Figure 1) are used in this study.

Within the past twenty years the number of geopressured gas reservoirs developed has been large enough to make a valid investigation.

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