A Systematic Approach to Developing Engineering Data for Fracturing Poorly Consolidated Formations

Abstract

Abstract This paper presents a methodology for acquiring the engineering data necessary to develop a successful fracture stimulation campaign in a soft unconsolidated formation. This methodology was applied to a zone containing highly laminated sand/shale sequences, in which the sands are unconsolidated and easily damaged. The methodology, however, could be applied to any zone. The zone of interest has historically produced at low rates and contains significant untapped oil reserves. Thus, it is an attractive candidate for fracture stimulation. The success of this new fracture program requires a fundamental understanding of reservoir properties and, necessarily, an efficient method for obtaining those properties. To fulfill such a need a systematic data development procedure was formulated and implemented. This paper provides the reader with an understanding of the tests conducted the interpretation of the data, the design approach taken, the operational activities, and the resultant well performance. Introduction In April 1996, Thums Long Beach Company embarked on a program to fracture stimulate a highly laminated but unconsolidated shale/sand stone sequence. All prior completion and stimulation techniques were unsuccessful in yielding significant oil production from this zone. These unsuccessful completion attempts consisted of various open-hole and cased-hole gravel packing scenarios coupled with non-damaging drilling fluids and post-completion acid stimulations. The unsatisfactory productivity of these completions and the considerable remaining reserves in this zone are the impetus for this fracture stimulation program. The zone of interest is the lower half of the Ranger Zone in the Long Beach Unit of the East Wilmington Field. The Long Beach Unit of the East Wilmington Field lies under and immediately off the coast of Southern California adjacent to the City of Long Beach (Fig. 1). The productive areas of the field cover 4900 acres (1983 ha). The Wilmington Field was discovered in the 1930's but development of the offshore portion of the East Wilmington Field was not initiated until 1965 with the construction of the Long Beach Unit oil islands. The Long Beach Unit of the East Wilmington Field is composed of three major producing zones: the Ranger. the Terminal. and the Union-Pacific-Ford. Each is part of a northwest-southeasterly trending anticlinal structure that is highly stratified with interbedded shales and sandstones (Figs. 2 and 3). P. 233^