PRESSURE TRANSIENT ANALYSIS IN UNCONVENTIONAL RESOURCES

摘要

The term unconventional gas refers to coal bed methane (CBM) and shale gas and in this paper the testing of wells will be addressed. In the CBM case testing is either in the form of a rising liquid level (slug) test or a mini-DST using a wireline formation tester (WFT). The determination of permeability, skin factor and pressure allows dewatering rates to be predicted. In shale gas the analysis of production data, obtained at approximately constant bottom-hole pressure, allows the determination of the enhanced permeability of the natural fracture network occasioned by the slick water treatment. In both situations the effect of stress on permeability is important but difficult to quantify. The main evidence is that production rate can be increased by reducing drawdown - this is only explicable in terms of pore pressure dependent permeability. A pseudopressure approach is proposed to allow pressure transient data to be analysed and well deliverability to be optimised.