Inert Gas Injection as Secondary and Tertiary Recovery Method in the Martha Field in Kentucky

Abstract

Abstract To study the economic feasibility of an inert gas injection process in the low-permeability portion of Martha field, a pilot project was portion of Martha field, a pilot project was initiated in Dec., 1966. During 3 years of operation - from 1967 to 1969–77 MMscf, or 20.6 PV, of inert gas have been injected into the formation. PV, of inert gas have been injected into the formation. As of this date, approximately 12,000 bbl of additional oil have been recovered. Another 5,000 bbl of "inert gas oil" are expected before the production declines back to its initial rate. Calculated additional oil recovery is about 33 bbl/acre-ft. Inert gas injection per barrel of oil production amounts to approximately 4.5 Mscf. Before going to a full-scale injection program, a second pilot was initiated to study the effectiveness of this process, in combination with cross flooding, in process, in combination with cross flooding, in a watered-out low-permeability area where waterflooding was ineffective. First results obtained are encouraging. The cost for generation and compression of inert gas is estimated to be 120/Mscf. Introduction Eastern Kentucky is one of the old oil-producing areas of the U.S. The first known well to produce petroleum was drilled in 1830 in Knox County. Fig. 1 shows geographic locations and geological formations of main oil- and gas-producing areas of Kentucky. The Martha oil field is located just northeast of the junction of Johnson, Lawrence and Morgan Counties, and is shown with an arrow in Fig. 1. The field was discovered in 1919 and covers approximately 4,500 acres. Since then, the Martha oil field has produced roughly 19 million bbl of oil primarily by gas-in-solution type reservoir energy. As the reservoir energy declined, a waterflood project on the east side of the field was started in 1955. As of this date, approximately 2,300 acres in the main area of Martha field has been developed for and is presently maintained under active water injection. Over 6 million bbl of secondary oil has been recovered during the last 15 years. The expansion of waterflood to an additional Ashland-owned 1,100 acres was limited because of low injectivity. This low-permeability portion of the Martha field has produced 4.7 million bbl of primary oil, which represents roughly 127 bbl/ acre-ft, or 15 percent of initial oil in place. In other words, over 30 million bbl of oil remains unrecovered in the ground. This huge amount of oil is a big challenge to us and offers an opportunity to test the field-wide application of one of the improved oil recovery techniques.