This paper discusses improvement in production rates of shallow gas wells through the use of improved low-temperature breaker technology. Systematic field evaluation has shown that the use of a new breaker system has increased well production in spite of inherent problems in the area due to severe proppant embedment. Previous use of an encapsulated breaker (EB) designed for well temperatures above 50 ºC had shown production improvement over conventional dissolved breakers. The current study has shown that the new breaker system, specially designed for temperatures <50 ºC and closure stress <7000 kPa has been able to improve production by an additional 15 to 22% in direct offset comparisons. Study criteria included selection of a suitable area offering the ability to maintain consistent drilling and completion programs with the primary variable to be the breaker system used. This paper also discusses laboratory development of the new breaker system including effects of temperature and closure stress on barrier properties, and fracture conductivity comparisons.
Workovers and increased shallow drilling activity have stimulated continued interest in methods to improve the performance of low-temperature wells.1 Published data have shown improvement in these wells using encapsulated breakers; 2 however, typical low-temperature conditions require that the breaker design be optimized to ensure achieving maximum efficiency/cost effectiveness. There is a significant amount of published literature regarding laboratory and field studies on the application and use of delayed release breakers from low to high temperature gas well conditions.2,4 However, there has been little if any systematic comparison of different encapsulated breaker designs on actual well production. This study specifically shows how optimized encapsulated breaker technology can significantly improve shallow gas well production. It also shows how a field evaluation can be accomplished in an area of typical marginal economics, provided prior planning in well selection and adequate study design are done.
The shallow gas sands of southeastern Alberta contain significant gas reserves;5 however, due to the general low quality of the pools, cost-effective optimization of gas production through the application of available stimulation technology has been very difficult. Primary producing formations include the Milk River formation, Medicine Hat sandstone and Second White Speckled shale (Second White Specks) (Fig. 1 and 2). These reservoirs were discovered as early as 1883,6 when the Milk River A gas pool was struck while the Canadian Pacific Railway was drilling for water west of the city of Medicine Hat, Alberta.
Development of the reservoirs has continued up to the present time, where application of more contemporary technology has aided in well productivity. Typical reservoir characteristics of these three formations are described below.
The Milk, River formation of the Upper Cretaceous region sits on the gray calcareous shales of the Colorado group. It is overlain by the Pakowki formation, a gray shale. Often, the Milk River is divided into upper and lower members. In Montana, the upper portion is referred to as the Eagle Formation, and the lower portion is called the Virgelle sand.