Seismic Reservoir Prediction For Formation PengLaiZhen Of Baimamiao Area In Northwestern Sichuan Basin

The study area locates in northwestern part of Sichuan province and is a substructure of LongMenShan structure region. Seismic exploration has been done for 6 times and interval between seismic line is 0.7 to 1.2 kilometers. Till January 2000, there are 37 wells whose object information is group Penglaizhen and depth of wells vary from 800 to 1500 meters. Among them, there are 22 gas wells, 13 wells which have a little gas and 2 dry holes and approximate 60 percent wells succeed. In Baimamiao area, there is 433 square kilometer area which have wells and controlled reserves reach to 391.76X10V.The paper study gas geology property of group Penglaizhen first. Based on this, my paper make more effort on a key point-reservoir description by using advanced seismic prediction methodology and information from geology, loggin, well testing etc. Key research results are shown as follow:1. Facies of group Penglaizhen are a combination of fluvial, delta and lacustrine facies and information of formation Penglaizhen can be divided to 3 facies, 6 subfacies and 14 microfacies.2. Moreover there are 5 sand groups in information of formation Penglaizhen (named A B C D and E from top to bottom). Sand group C which is good reservoir in study area distribute stabilely.3. There are 3 kinds of sand reservoir:A. High-porosity and good-permeability gas payB. Middle or low porosity and permeability pay with low abundant gasC. Shaly siltstone gas pay4. Gas productivity of formation Penglaizhen vary greatly and you can find high productivity reservoir (High-porosity and good-permeability), low productivity reservoir (middle porosity and low permeability) and tight sand(non-reservoir).5. Structure , lithology and caprock control gas reservoir in formation Penglaizhen and the axis of trap is a favorable belt to find gas becauseof good trap and reservoir. Seismic reservoir prediction study shows good reservoir condition in southern side of trap. For example, belt from well bq41 to bq30 is good place to find gas whose facies is delta plain and delta frontal.6. Application of each reservoir approach should base on geology and seismic data in study area. So it is important to study geological and geophysical properties of target first.7. In my paper we study logging and seismic response of gas layer first and then summarize characteristics of gas sand. After seismic inversion we predict thickness, net thickness and average porosity of gas sand in group Penglaizhen. Based on study mentioned above we can bring forward favorable targets which provide basis for upgrading reserve and locating new wells.8. Based on integral study sand group C which is more porous and permeable is the best sand in formation PengLaizhen.