HETEROGENEITY OF DEVONIAN RESERVOIR AND ITS MAJOR CONTROLLING FACTORS IN BACHU-MAIGAITI AREA, TARIM BASIN

Bachu-Maigaiti area in Tarim Basin is well known for accumulation of oil and gas, where oil and gas have been found in many wells in the Devonian reservoir. However, the uncertainty of forming conditions of favorable reservoir and distribution regularity hinders further exploration and development in the area. With observation of drilling cores, rock slices and casting thin sections of eight wells, combining with intrusive mercury analysis and porosity and permeability test, the authors study pore characteristics and non-homogeneity of the Devonian reservoir in the area. The results show that the main sand pore type is intergranular dissolution pore, followed by primary intergranular pore, with structural characteristics of fine pore, fine throat and poor sorting. In addition, quantitative parameters such as sandstone density and permeability variation coefficient show a strong heterogeneity between and within the layers of the Devonian reservoir in the study area. The degrees of heterogeneity are mainly controlled by genetic types of sandbody and diagenesis. The early oil and gas filling has only an indirect controlling effect on part of the area.