The Yangxin Series Carbonate Reservoir Fracture Seismic Prediction In The DTC Area In The South Of Sichuan Basin

The research area is located in Sichuan basin in the southwest of China which is an important gas production base. The oil and gas exploration of this area began with the founding of the initial stage and has experienced several decades. The Jurassic,Triassic and older Permian gas reservoir have be found from the shallow to the deep layer 。 With the progress of the oil and gas exploration in Sichuan basin in recent years,Permian Marine strata shows great exploration potential. the production Wells of the Yangxin series. in the gas field is closed nearly,So it is necessary to explore the remainder oil and gas resources of the Yangxin series.The reservoir lithology in this area is mainly dense limestone and has low porosity and permeability. Storage space is mainly made up of cracks.The slot-hole system formed by corrosion and tectonic movement is extremely complex.Some features of slot-hole system, such as: great disparity in size, shape variety, the different dates of origin and formation, bring some difficulties to prediction of oil and gas in this area.Firstly, used drilling, logging, coring and seismic data to analyze the Yangxin series reservoir geological characteristics in this paper. And then analyzed the seismic response characteristics of the slot-hole system on the seismic section through the seismic forward modeling and the old well seismic section in the survey and summarized the seismic methods for recognition principles of fracture-vug-developed zones.Using the random seismic inversion technology to predict the distribution of reservoir. Secondly, respectively, using post-stack seismic data attribute analysis technology and pre-stack fracture detection technology to predict and describe fracture-vug-developed zones. Using the spectrum attenuation technique and pre-stack AVO technique to evaluate reservoir fluid property. The application effect of various techniques compared with drilling and production data to achieve the goal of predict favorable reservoir area ultimately.The main understanding and conclusions that are made from research of fracture-vug-developed zones in the carbonate reservoir in the survey through theresearch work as follows are as follows:(1)To find the area where developed the fracture and dissolve corrosion pore atthesame time in oil-gas predict research of the survey is guaranteed to obtainindustrial oil and gas flow. The main reservoirs of this area is located in the MaoⅡand MaoⅢ segment of Maokou formation, which is a set of Marine carbonate strata,through analyzing drilling, logging, core and seismic data. The lithology is mainlypure and compacted limestone and deposits stably at transverse level. Matrixporosity and permeability are low, but the fracture permeability is high in thelimestone. Reservoir spaces are composed primarily of dissolve corrosion pores andholes. Cracks are penetrating channels(2)Seismic response characteristics of fracture-cavity body on the seismic section are obvious change of seismic velocity, amplitude and frequency. Seismic forward modeling and inversion analysis showed that speed of fracture-cavity body is less than the surrounding rock’s. The characteristics of seismic amplitude are the seismic events bifurcate and merger, interval transit time increases, waveform distortion,clutter or blank reflection, short axis wave crest and wave trough. When the seismic wave propagates in the fracture-cavity bodies where contain fluid, the he high frequency components will attenuation soon and Seismic dominant frequency will move to low frequency, so the frequency bandwidth becomes narrow(3)Seismic amplitude attribute is more sensitive to fracture, and the development of fractures in the Yangxin series is closely related to fault. It will get good effect that combined application of post- stacked coherence technique, curvature property and pre-stack p-wave azimuth anisotropy to predict fractured development zones on the basis of detailed construct map and fault distribution provided by seismic explorationThis paper proved the applicability and validity of the those methods based on he combination of reservoir seismic prediction method research and practical exploration in this area. Those methods promote the development of carbonate reservoir exploration in this area and also have accumulated rich experience to further research reservoir fracture identification for us.