Published in

SPE Hydraulic Fracturing Technology Conference

DOI: 10.2118/119481-ms

Links

Tools

Export citation

Search in Google Scholar

Increasing Reservoir Contact by Combining Mechanical Diversion and Unique Stimulation Chemistry

This paper was not found in any repository; the policy of its publisher is unknown or unclear.
This paper was not found in any repository; the policy of its publisher is unknown or unclear.

Full text: Unavailable

Question mark in circle
Preprint: policy unknown
Question mark in circle
Postprint: policy unknown
Question mark in circle
Published version: policy unknown

Abstract

Abstract The Edwards Limestone in South Texas often requires stimulation to be commercially productive. The relatively low permeability, high Young's Modulus, presence of natural fractures, minimal stress barriers to control height growth, and formation temperatures up to 375°F provide a challenging environment for a successful stimulation. Conventional stimulation approaches using acid fracturing and proppant fracturing techniques often have resulted in less than optimal effective etched or propped fracture half lengths, respectively. Horizontal openhole completions have increased the potential reservoir contact to the wellbore, but are not effective without stimulation. Achieving the diversion along the horizontal wellbore that is required to effectively treat the entire interval proved difficult using conventional diversion techniques with particulate and chemical diversion. Furthermore, the difficulty in achieving sufficient fracture width limits the proppant concentration that can be pumped into the formation. Acid fracturing was a desirable stimulation technique, but because of the high reservoir temperature and associated high acid spending rate, it was difficult to achieve a long effective etched half length with acid fracturing. A unique approach was developed by combining a novel diversion technique with a new stimulation treatment. The diversion technique enables mechanical isolation of the openhole completion during the stimulation treatments. The mechanical diversion system also facilitates efficient pumping of multiple stimulation treatments, resulting in increased reservoir contact to the wellbore. The new stimulation treatment uses a unique lightweight (1.25 SG) proppant-like material that is pumped into the well as an inert substance. The product hydrolyzes only after the solid particles are in the reservoir for an amount of time at temperature. This enables the fracture etching process to occur during shut-in and flowback of the well thus solving the problem of creating long effective etched fracture half lengths with acid. The combination of these two techniques has enabled a much larger stimulated reservoir contact to the wellbore in the Edwards Limestone in South Texas, which leads to improved production. Introduction The Edwards Limestone reef trend is a natural gas play that runs from South to East Texas with a northeasterly trend. The productive section in the Bee, Karnes, and Dewitt tri-county area is part of the greater Stuart City Reef Trend (Fig. 1). A detailed geological description is discussed in the next section. Geology The Edwards formation consists of fossiliferous limestone that was deposited in a complex of related environments that include biogenic reefs, banks, tidal bars, islands, and channel fills developed along the basinward edge of a carbonate shelf. The shelf almost completely encircled the ancestral Gulf of Mexico during the Early to Middle Cretaceous period. The reefal buildups, which developed along a high-energy shelf margin, were able to maintain their growth positions against a rapidly rising sea level that resulted in vertical accretion. A depositional break in slope developed basinward of the reef systems as insufficient sediment accumulated beyond the reefs resulting in a distinct shelf edge. The Edwards Limestone conformably overlies the Glen Rose Limestone, which together makes up the Stuart City, and is approximately 2,000 ft thick. Separated by the Pearsall Shale, which is approximately 460 ft thick, is the underlying Sligo Limestone. The Edwards Limestone is overlain by the Georgetown Limestone in varying thicknesses up to 95 ft; it is in turn overlain by the Eagle Ford Shale as shown in the stratigraphic column in Fig. 2 (Wooten and Dunaway, 1977).