Abstract

A water alternating gas project was started in late 1985, south of Lloydminster in section 06-049-27 W3M.

Waterflooding, as well as water alternating gas injection, have been evaluated in the laboratory. These tests demonstrated that a methane WAG process would be effective in increasing the oil recovery in section 06-049-27 W3M. Recovery over primary is predicted to be 5.5%.

Considering the thin net pays of the Sparky "B" and lie" zones (approximately 3 meters each), the underlying water in Sparky "C" zone and the existence of a shale barrier, thermal recovery techniques were not feasible in this location.

Introduction

The Silverdale Sparky Pool is located in the Lloydminster area of Western Saskatchewan and Was discovered in 1945 (see Figure 1). Development drilling of section 06-049-27 W3M began in mid-1977.

Section 06-049-27 W3M is 100% owned and operated by Home Oil Company Limited.

The formation is a typical Sparky with good porosity (29%) and high oil saturation (82%). Before the implementation of the water alternating gas (WAG) scheme, primary production from section 06 was completely depleted.

A WAG project has started in late 1985 and is composed of 3 patterns; two inverted 6-spots and one inverted 5-spot joined in the north-south direction.

Low oil prices and a shortage of injection water have plagued the project over its first year of operation. It's too early to determine the effectiveness of WAG, but production is encouraging.

GEOLOGICAL DESCRIPTION OF SECTION 06-049-27 W3M

In section 06-049-27 W3M ~he producing horizon is the Sparky formation of Lower Cretaceous age. The formation is divided into two sand zones, Sparky Band C, separated by two thin shale beds.

The average net pay of the Sparky Band C is 2.6m and 3.3 meters respectively.

Figures 2 and 3 are structural contour maps of the Sparky Band C sand respectively. The structure rises slowly towards the east for approximately 2-1/2 LSD's, then is abruptly cut off due to a shale barrier runing north/south. The Sparky B sand has an additional geological feature, a shale channel runs diagonally NW/SE. Consequently the B zone is shaled out in a number of wells, notably 2B-6, 2C-6, 6A-6 and 6C-6.

Two wells have been cored through the section (2C-6 and IOC-6). Above the B sand is a coal bed of approximately 1.5m in thickness. The coal discovered was black, brittle and of bituminous nature.

The pay zones generally consisted of dark brown, poorly consolidated, fine to medium grain, round and well sorted sand grains with excellent porosity and permeability.

Average water saturations for the Band C zones were 20% and 17.5% respectively. The shale interbeds encountered were generally medium gray to black, soft and non-calcareous, often containing minor sandstone lamina. A sieve analysis and x-ray diffraction analysis was carried out on a sample from 2C-6. The sieve analysis revealed that anywhere from 1%-2.4% of the sample was clay (less than 5 microns) material. The x-ray diffraction analysis showed that kaolinite, illite, chlorite and smectite were the only clays present.

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