The prediction and comprehensive evaluation technique of carbonate reservoirs: An application in oil and gas reserve of Ordovician in buried hills of Sangtamu area

摘要

The discovery of the oilfield which has about billion tons of reserve in the south edge of Tarim basin and the breakthrough of many wells including No. 54 achieved in the south edge of Sangtamu area took the oil and gas exploration into a new stage In Sangtamu area. But one key problem which significantly restrains the oil and gas exploration is the inhomoge-neous character of reserving layer in this region. Comprehensive use of geology, well logging, datum of seismic and fine description distributing characteristic of crevice and cave to forecast and comprehensively evaluate seismic reserving layer is the key to efficient exploration and development of the oil and gas field. In the 3D dataset, with seismic horizon flattening and 3D-visualization, we can probe the controlling function for karst of ancient structure and ancient water system; the lateral variations of reservoirs using the amplitude and frequency changes produced by crevice and cave reserving layer's absorbing and attenuation to the seismic energy; the low velocity anomaly of crevice and cave system using seismic and logging united inversion technology; and the scattering and diffraction of seismic wave because of crevice and cave using coherent cube technology and with the strain quantity analysis technology to forecast the cave and crevice developed area. From the comprehensive evaluation of all these, we find that the reservoir layer centralized vertically between 40 to 120m under the water table and horizontally developed near ancient river course, joint of salt water and fresh water and the fault-developing area. The exploring result of the well 171 verified the rationality of this forecast and established a foundation for efficiently exploring and developing oil and gas field in this region.