Abstract

Primary production from the Tangleflags North Lloydminster sand in the steamflood project area commenced in 1982. Despite encouraging initial oil rates, rapid water coning rendered operations uneconomic with recoveries of less than 1% of oil-in-place. The area is underlain by an extensive aquifer and oil viscosity is 13,000 mPa.s. This paper describes preliminary feasibility investigations and the results of a steamflood field pilot which commenced operation in late 1987. Discussion of operating experience including well design considerations, is included. The project has recently been expanded Gild now includes two horizontal producing wells and Jive steam injectors. Performance to date is encouraging and agrees well with early numerical model predictions.

Introduction

The Tanglenags North field is located twenty-two miles northeast of the city of L1oydminster, as shown in Figure 1, and has been producing heavy oil since 1977. Development of the Lloydminster sand reservoir initially took place in the vicinity of the discovery well at BlO-1O-52-25 W3M. Drilling to confirm an extension of the channel sand trend to lands north of the North Saskatchewan River was carried out during the period 1982 to 1985, delinealing what is now designated as the steamflood project area. Despite generally good initial oil productivity, primary recovery has been poor due to rapid coning in of water from the underlying aquifer. High water cut and resulting poor economics have resulted in the suspension or abandonment of all but one vertical primary producing well in the steamflood project area. Recovery to date by the vertical wells has amounted to only 0.6% of the original oil-in-place. Well performance and recovery status for the project area wells is summarized in Table 1.

Excellent pay thickness and reservoir quality in the Lloydminster zone led to consideration of steam injection methods to improve recovery efficiency, although the presence of a bottom water zone and a gas cap represented significant obstacles. Preliminary work in the form of a cyclic steam injection test, laboratory core floods and numerical reservoir simulation, led to the drilling of a horizontal producing well in the fall of 1987. Steam injection through an array of vertical wells commenced in June of 1988 and a second horizontal producing well was added in the fall of 1990. By the end of May 1991, cumulative oil production from the project was 151,200 m3 (951 MSTB) and a peak monthly oil rate of 370 m3/d (2330 B/D) had been achieved.

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