The structure of crushed zone near the Lungudong strike slip fault and its relationship with the gas and oil

Using the latest seismic data of 300 km² depth migration before stack in Lungudong, the authors identified three stages and four groups of fractures in Lungudong gas field by various means. The strike and compactness of the fractures are controlled by faults. The fractures are mainly high angle(45°-75°)narrow fractures. Corrosion is developed along the fractures, and the dominant strike is NE-SW. In the longitudinal field, the fractures of Yijianfang Formation has maximum density(14 fractures per 100 m), followed by the compactness of the fractures of Yingshan Formation (6 fractures per 100 m) and the compactness of the fractures of Lianglitage Formation (4 fractures per 100 m). In the plane field, fracture is mainly distributed in the area within 1 km of the main faults. With the increasing distance from the fault, the degree of fracture development (linear density of fractures) decreases with the tendency of index number. On such a basis, the authors have comprehensively considered developmental characteristics of main fractures and accompanying fractures. In the plane field, crushed zones of Lungudong fault are divided into pinnate crushed zone, transform crushed zone, echelon crushed zone, and composite crushed zone. The area of pinnate crushed zones is the largest and most gas and oil spots are concentrated here, and high-efficiency wells are centrally distributed in this area at present. The exploration drill holes around the pinnate crushed zone offer a new train of thought for the study of strike slip fault controlling oil and gas reservoir and finding new rich domains of gas and oil.