Reservoir Containing Gas, Multi-property Prediction Techniques

With the further development of oil exploration in the world, oil and gas reservoirs which easy to find are less and less, exploration targets gradually moved from large-scale structural reservoirs to small-scale structural and lithologic reservoirs. There are many problems in these small-scale structural and lithologic reservoirs in processing and interpretation. This paper focuses on the difficult problem on exploration and development at a block of sandstone Sulige Gas Field. AVO attribute inversion and earth's absorption and attenuation effect are used to predict gas reservoirs.First, this paper introduces the basic principles of AVO technical and earth's absorption and attenuation effect and the rock physics, including Zoeppritz's equation and the different types of its approximate equations. Approximate equations of Zoeppritz is analyzed to understand their specific applications. Second, this paper introduces several common methods of AVO inversion, which focuses on the method of AVO attribute inversion, including its theoretical reasoning, processing, and the production of P-wave, S-wave, Poisson's ratio and other properties profile. Third, based on two-medium model, calculated the reflection coefficient of four kinds of gas-bearing sandstones by Shuey's approximate equation, then simulate and analyze AVO response of its corresponding features, in order to determine which kind of the sandstone in the Gas Field. Finally, this paper analyzed pre-stack data by the methods of AVO attribute analysis, introduced sophisticated methods of pre-stack processing.The sophisticated pre-stack seismic data processing provide a high-quality pre-stack gathers for reservoir prediction, Based on the research of different angle gathers, formed a set of near-offset stacked section and far-offset stacked section with AVO characteristics. Poisson's ratio, absorption coefficient and other properties are obtained by AVO attribute inversion and the method of absorption and attenuation reservoir prediction, and set up a variety of property crossplots. On the purposes of more accurately predict reservoirs, identify the best response properties of gas-bearing sandstone and set up a AVO attribute detection standards of gas-bearing sandstone by comparison of various property crossplots.This paper took the prestack seismic data from Sulige gas field as an example, the property profile obtained by AVO attribute analysis, combined with the known drilling data, set up the detection standards of reservoirs, which provide the basis for future well spacing and has certain positive significance.