Reservoir Prediction And Fluid Detection Technology Research Of Xujiahe Formation In The Longnvsi Of Middle Sichuan

The structure has experienced50years of exploration in the Longnvsi of centralSichuan basin, in the Xujiahe formation we has been found good hydrocarbon show,but has not obtained the exploration results, the main reason is due to a lack of highprecision3D seismic data, which led to us can’t accurate understanding of the form oftectonic traps, so, we can’t work for reservoir prediction that base on the seismic.Basing on the3D seismic data, firstly, we interpret the3D seismic data, anddemarcate geologic horizon accurately, find the fault location in the top of the secondand fourth member of Xujiahe formation; we should find out the reflection horizon’sstructural configuration details, size and high position in the Xujiahe formation. Thenwe use small fault interpretation technique, coherence technology, the maximumentropy spectrum analysis technology and curvature attribute technology for detectionof fault distribution in the fracture development zone, especially the distribution ofsmall faults; Secondly, we use the post-stack seismic inversion technique (Includingbroadband constraint inversion and geostatistics inversion) and pre-stack seismicinversion technique (Based on the Knott-Zoeppritz equation inversion technique) forreservoir prediction, and use wavelet reconstruction technology for detection of thefluid in the study area of the second and fourth member of Xujiahe formation; Finally,we have delineated the favorable exploration zones in the studied area of the secondand fourth member of Xujiahe formation on the basis of factors such as: consideringthe structure, degree of fracture development, reservoir prediction and fluid detection,which provided the powerful technical basis for natural gas exploration in the studyarea. This paper’s main results are as follows: 1. The Longnüsi structure as a whole as a development on the upper palaeohighsiltstones compression torsion stress control rolling anticline, and its structure axialfrom west to east and from north west to the east; It has more than one local trap onthe structural high part of the development that most traps controlled by fracturesignificantly, with sinistral oblique crack distribution characteristics, and from thesecond to the sixth member of Xujiahe formation has obvious inheritance; Thestructure of north and west was influenced by fracture formation and then formed skirtdifferentiation, south side is relatively simple;2. By the dragon female temple area’s3D pre-stack time migration data to carryout the fine structure interpretation, the top boundary of the second member ofXujiahe formation were found and implemented all kinds of structural trap, a total of18, trap with a total area of about41Km2, and the fourth member were found andimplemented all kinds of structural trap, a total of17, trap with a total area of about44Km2;3. We have been implemented4small faults development zone by curvature andsmall fault interpretation technique. The small fault zones is mainly distributed inlarge fault or the interchange of two groups of fault; the second member of Xujiaheformation’s minor fault is more developmental than the fourth;4. The core physical statistics analysis shows that the second and fourth memberof Xujiahe formation of Longnvsi district belongs to low porosity and lowpermeability reservoir, and the fourth is given priority to with porosity, while thesecond is porosity and fissure-porosity. So the fourth’s physical properties isrelatively well in the second’s;5. The second and fourth member of Xujiahe formation of the study area aremainly delta facies; In the sedimentary period of the second member’s lowersubmember of Xujiahe formation, the middle of study area’s main channel is mostdevelopment. But in the fourth, the scale turn smaller obviously; The main channel ofthe fourth member has been inherited the second member, which developed in thecentral area and the scale was larger than the second member’s;6. The second member of Xujiahe formation’s pore type development reservoirwas mainly located in the Nv88-1wellblock, Nvshen1wellblock and Nv110wellblock. We predicted the gas-bearing sandstone is mainly distributed in theNvshen1wellblock, Nvshen002-1wellblock, Nv88-1to Nvshen002-4wellblockand Nv110wellblock; The fourth member of Xujiahe formation’s favorable reservoirand gas-bearing sandstone mainly developed in the central area; By interpreting the tectonic characteristics, the small fault development degree, thedistribution characteristics of sedimentary facies, reservoir inversion, reservoir andcap rock combination, accumulation analysis, fluid prediction, etc, factors tocomprehensive analysis and research, and then we optimized the tectonic belt fromNvshen002-4well to Nvshen002-1well, from Nvshen1well to Nvshen2well andNv110well, etc, as the three favorable exploration zone in the study area of thesecond and fourth member of Xujiahe formation. On the basis of favorable explorationzone division, we make a comprehensive research and analysis about the important trap, and combine with the reservoir development and reservoir analysis. Finally, we puts forward10key exploration targets.