Results of a Field Test to Determine the Type and Orientation of a Hydraulically Induced Formation Fracture

Abstract

Abstract The planning phase of a program for expanding a shallow waterflood project was stalemated by lack of knowledge concerning the type and orientation of hydraulically induced formation fractures. Profitable development of the project is known to depend on successful fracture stimulation. To obtain in situ data about the induced fractures, a simple, downhole, impression sensing test was devised using an inflatable formation packer as the basic investigating element. A new well was hydraulically fractured, after which the formation packer, equipped with an especially sensitive rubber cover, was set in the pay interval. A perfect impression of the previously induced fracture was retained on the packer element. This impression showed that the fracture was vertical, oriented north 730 east, and present along the entire 9-ft section of impression rubber. Prior to the down-hole test, fracture orientation and type had been predicted based on published theories describing the relationship between tectonic stresses and artificial formation fracturing. The test data verify these predictions. As a sidelight, it is concluded that deep notches in the pay sand do not cause horizontal fractures in this area. Introduction The technical literature of recent years contains many papers which attempt to provide insight concerning the type, orientation and fluid- carrying ability of hydraulic fractures. Theoretical methods have been proposed with which the field engineer can make optimum use of artificial formation fracturing as a stimulation technique. The purpose of this paper is to describe an attempt to corroborate theoretical concepts so that combination waterflood-fracture stimulation program could he exploited to maximum advantage. The area involved is that bounded by Mobil Oil Co.'s Chalk Waterflood project which is located in the Howard Glasscock field of eastern Howard County, Tex. Production is from the 1,600-ft Queen sand of Permian age. This sand possesses an average porosity of 23 per cent, an average permeability of 57 md, an average water saturation of 35 per cent and an average gross thickness of 25 ft. The sand is very fine-grained and contains considerable amounts of gypsum, silt and clay. Geologically, the project is situated on the Eastern Platform of the Midland basin. Fig. 1 is a map showing the project area. The Chalk flood has been in operation since 1947; however, results were generally discouraging. JPT P. 463^