Northern California Gas Sands — Hydraulic Fracture Stimulation Opportunities and Challenges^

摘要

Hydraulic fracturing is a stimulation technique successfully applied in formations throughout the world to increase production rates and enhance hydrocarbon recovery. The process involves creating a crack by pumping fluids at pressures above formation fracturing pressures, and then filling the crack with proppant to create a high conductivity connection to a large formation area. Hydraulic fracturing stimulates production by overcoming restrictions imposed by formation permeability, drilling and completion damage, production-induced damage and, an incomplete reservoir connection across laminated intervals. The process has been applied to a large scale in many Central and Southern California fields to enable economic development and reasonable hydrocarbon recovery. Example formations include the Belridge Diatomite, Stevens Sands, Etchegoin, Antelope shale, McLure shale, McDonald shale, Point of Rocks sands, Kreyenhagen shale, Ranger sands, the UP Ford shale, and the Monterey shale. Despite the routine application of fracturing in many fields, there has been very little fracturing experience in the gas-producing formations of Northern California. Example formations such as the Martinez, Forbes, Winters, and the K-1 are generally laminated sand intervals with low to moderate permeability (less than 1 mD and up to 10 mD), that are easily damaged by completion and production operations. Despite the hydraulic fracturing potential for stimulating production rates, improving gas recovery, and increasing reserves by extending the economic development area, it has been only sparingly employed. General formation properties are reviewed – what are the implications for hydraulic fracture potential, treatment design and placement challenges? Several treatments are reviewed to provide examples of fracture treatment behavior and response. Based on the initial experience and formation properties, it is believed that hydraulic fracturing has a significant potential in many Northern California gas reservoirs.^