Meadow Creek Unit Lakota "B" Combination Water-Miscible Flood
Authors: Gernert J.M. , Brigham W.E. 
Published: December 2007

The Meadow Creek unit Lakota "B" reservoir was subjected to LPG cycling, repressuring and miscible slug flooding with water injection. The last two steps are reported in this paper. This field case history covers the reservoir properties, primary production history, the miscible project including history of repressuring and of LPG- water and gas-water injection. Inherent problems in the Lakota "B" reservoir were paraffin and carbonate deposition, and several were related to the miscible flooding method used. Down-hole pump freeze-ups, heavy paraffin deposits on the downstream side of the gas separators and low treating temperatures were caused by the cooling effect of LPG as it expands under reduced pressures. The success of the operation is indicated by the fact that the flood will probably recover 13 per cent more oil than would have been recovered under water flood.

Introduction

Improving oil recovery has been the subject for much research and field experimentation in the past several years. Incentive for this increased activity is the realization that large amounts of oil still remain unrecoverable after using present knowledge and methods. Many new techniques are being tried, but those currently most popular are the miscible displacement processes. There are basically five types of miscible displacement processes:

high-pressure gas drive, enriched or condensing gas drive, LPG slug drive, LPG cycling, and alcohol slug drive.

In addition the first four methods may be improved by injection of water along with or after the miscible fluids. The process being used in the Meadow Creek Lakota "B" reservoir is the LPG slug drive augmented by injection of water in alternate slugs with the miscible fluids. These LPG-water slugs were originally followed by ethane-rich gas and water in alternate slugs; however, lean residue gas and water are presently being injected. This particular project has taken place in three phases. The first was LPG cycling, the second was repressuring the reservoir, and the third is miscible-slug flooding with water injection. This paper discusses the second and third phases of this project. The first phase was discussed in an earlier paper by Harbert et al.

Reservoir Properties

The Meadow Creek unit Lakota "B" reservoir covers approximately 350 acres. Pressure surveys, liquid levels, production histories and detailed log studies indicated that the Lakota "B" consists of two sand sections separated by a 10-ft shale break. The lower section is generally tight and primarily water productive, thus the majority of the production has come from the upper section. For individual data on the reservoir and reservoir fluids refer to Tables 1 and 2.The structure is an anticlinal fold trending northeast- southwest. A large normal fault cuts the Lakota formation north of Well 26 with a strike bearing approximately N 67 deg. E, dip NW at 50 deg. (Figs. 1 and 2). Oil was present in wells on the west side of the other possible fault shown in Figs. 1 and 2; however, the pay section to the west was thin, tight and commercially non-productive.

JPT

P. 993ˆ