Study On Fracture Of Carboniferous Volcanic Reservoir In 9～(th) Area, Kramay Oil-field

The 9th area, Kramay oil-field, lies between Bai Jiantan area and Bai Kouquan town, Kramay city, in the middle of Kramay-Wuer river' great overthrust fault zone ( or Kramay great fault ) that is in the northwest of Junggar basin, and in the south of Bai Jiantan-Bai Kouquan which lies between Bai Jiantan fault and north Bai Jiantan-Bai Kouquan fault in textural. It is a frontal block felt that belongs to Kramay great overthrust nappe structure. The Carboniferous volcanic reservoir is very rich in which rich hydrocarbon reservoir is found. The volcanic matrix has worse porosity and permeability and has very obvious heterogeneous feature, so fracture is the main channel and place in which oil and gas migrate and accumulate. Early study finds that volcanic fractures distribute very involute. This paper studies fractures of researched area firstly by using drilling material, core material and logging material, then predicts comprehensively fractures of this researched area by simulating tectonic movement and palaeostructural stress field, and finally analyses validity of these fractures, associated with study of modern earth stress.Then the following some knowledge is given:1) Fractures of volcanic reservoir in researched area are very rich, and they are developed in almost all volcanic reservoir to different extent.2) Volcanic reservoir has many types of fractures, but structural fracture is the main category. In addition, volcanic diagenetic fracture is developed to some extent.3) Four stages structural fractures are developed in volcanic rock mass, as is corresponding to tectonic movements. These fractures which are formed in different tectonic movement stage have different feature. Of them the fractures which were formed in the second stage (the late Hercynian movement) and the third stage (the Indosinian movement) have greater scale, especially of which were developed in the late Hercynian stage because of nappe structural movement have the best scale. The fractures which were developed in early stage (the middle Hercynian stage ) have small scale and low obliquity.4) Fractures' extensional directions are mainly to northeast-southwest, to which the fractures have greater scale, higher obliquity and basically accordant extensional direction with fault, and next to northwest-southeast.5) Fractures are mainly middle and low obliquity fractures. High angle fractures ( > 50? are mainly to northeast-southwest, next to northwest- southeast.6) Packed degree of fractures is higher. Excepting that the degree of the fractures which were developed in the fourth stage (the Yanshan stage ) tectonic movement is a little worse, other fractures are basically packed by different kinds of mineral.7) Plane distribution rule of fractures: the fractures mainly distribute nearby fault on plane, especially in the cross position of faults, such as nearby Gu-42 well. In addition, fractures that are developed in the fault block of Gu-16 well are more developed in the middle area in which is near to the fault of Gu-42 well, while the degree of fractures in the south and west area are correspondingly lowest.8) Validity of fractures is worse, but natural fractures that extend to the direction of 1000 perhaps splay to some extent, as is useful to migration of hydrocarbon.