The Application Of The Technology Of Space Grid Variable Velocity Mapping In The Study Of Superdeep Microstructure:A Case In The Tazhong No.1 Gasfield Of Tarim Basin

Block TZ62 of the No. 1 gas field is located in the eastern section of large reef of oil-gas reservoirs in slope break belt of central Tarim Middle-Late Ordovician.Reservoirs (average buried depth﹥5000 m)on the longitudinal growth developed in a range of 150 meters away from the carbonate rock roof.On the horizontally growth,reservoirs was quasi-layered and contiguous. Currently, the main technical bottleneck of development to increase reserves and production is how to reliably implement microstructures by means of effective variable velocity mapping. This paper focuses on exploring a method of variable velocity mapping in super deep microstructure and its application on the TZ62 block. The technology of space grid variable velocity mapping includes quality evaluation of basic data, speed factor analysis, space grid velocity modeling and quality control, etc. At present, due to the collection and processing problems, there are errors, whether from the seismic stacking velocity or logging speed variable velocity mapping. Among the influencing factors, T0-layer and drilling-stratification are more reliable than stacking velocity and logging speed. Based on the analysis on target horizon of block TZ62, by fitting the Three-Dimensional relationship of velocity and T0, we use the variation function of space grid to build the velocity model. Through the blind Shaft check and application analysis control the quality of velocity model and establish accurate velocity model. According to the time-depth conversion we get reliable fine structure that is suitable for block TZ62. At the same time we get three aspects of the effection: (1) Blind Shaft error is significantly reduced (structure error decreased to within10m from 15~80m), (2) Structural map is more consistent with T0 map in the trend and the microstructure is more accurate, (3) Microstructure and drilling is more matching, structural high place has high gas-oil ratio, oil, gas and water in reservoir distribute whole by the microstructure control.