Xu Zhengyu
Zhejiang Oilfield Company, PetroChina
Title: Longmaxi formation shale gas sweet evaluation and optimization in the Upper Yangtze Region
Biography
Biography: Xu Zhengyu
Abstract
The upper Yangtze region has experienced multi geological events, and there is characteristic of high evolution and strong transformation of the marine shale. So that the shale gas accumulation is very complex. By the comparison of North American and the upper Yangtze shale, Longmaxi formation organic rich shale of the Upper Yangtze Region is older, higher degree of evolution, but the sedimentary environment and lithology basically is the same as North American Barnett shale. Due to Longmaxi shale experienced multi deformation and different burial environment, its hydrocarbon has entered the over-mature stage. North American tectonic is relatively stable and its shale is still in the middle- high mature stage. The upper Yangtze shale gas accumulation and preservation are controlled by the reservoir pore pressure and the sealing of the accumulation unit. Combined the Longmaxi shale reservoir and the stratigraphy deformation characteristics of the upper Yangtze region, the shale gas sweet is controlled by deep shelf anoxic face and structure transformation and adjustment zone. Recently, all of the found Longmaxi shale gas reservoirs locate in gentle wings and axis of residual syncline of the zone. And a series of identification technologies of the shale gas reservoir and prediction technologies of sweet distribution have been summed in the upper Yangtze region. Longmaxi shale gas layer takes it as a feature : high gamma, high acoustic time difference, low P-wave and S -wave velocity ratio, and with high resistance, low density, low compensation neutron anomaly. The Longmaxi sweet layer appears" low frequency wave impedance reflection and AVO anomalies". The structure transformation and adjustment zone shows the multi-source convergence and natural net-fracture reservoir conditions, therefore good accumulation units of syncline belts become shale gas high production in the upper Yangtze region marine. Therefore Longmaxi shale gas sweet is controlled by deep shelf anoxic face and tectonic transformation and adjustment zone in the upper Yangtze region.
