Application Of Production Seismology Interpretation Technology To Oilfield Adjustment Stage Under Dense Well Pattern Condition

With development of Daqing Oilfield having entered the later stage of high water cut the remaining oil prediction has become the core problem of oilfield development and the bottleneck of EOR. The key problems of controlling the remaining oil distribution are structures with micro amplitudes, small faults and sand-body distribution between wells. Without 3D seismic data structure interpretation and reservoir prediction are conducted on the basis of well portray and prediction, lacking objectivity and accuracy; in the case of the well pattern density of 50～55 well/km~2 the understanding degrees of sand body can only reach 60%～75%, breakpoint combination is only about 85%, which are the core contents of development seismology interpretation technology under dense well patterns.Taking Lamadian Oilfield of Daqing as an example, on the basis of development seismology processing achievements and theoretic researches, combining with logging information and structure interpretation, and combing with comprehensive application to forward simulation, geological horizon calibration from P and S-wave combined seismology, many methods of recognizing small faults, taking increase of interpretation accuracy of small faults and structures with micro amplitude and prediction accuracy of sand bodies between wells as the goal, through tests of interpretation methods of small faults and structures with micro amplitude under dense well patterns and inversion parameters from reservoirs under deferent condition and analytical study of seismic attribute system, this paper realizes recognition of faults of 3m and accurate recognition of faults of 5m; the prediction accuracy of thin sand bodies is high, and the error of structural interpretation is about 1m. The paper also presents the structural interpretation and the reservoir prediction suitable for the dense well pattern condition. Main achievements and innovation pointsare as following:(1) The methods of recognizing small faults are improved further. On the basis of thecalibrated technology for P and S-wave combined horizons, taking P-wave data as the dominant factor, using techniques, such as coherent body, ant body, S-wave combined horizon tracing, time to depth conversion of special variation 3D velocity field, using converted wave and well breakpoint data for guide, using dynamic data from well points as posteriority, and using data from interference test wells to ascertain, the special combination structure of faults are made more reasonable, the accuracy of recognizing small faults above 3m is risen, the error of posterior wells is smaller than 0.2%. (2) The clue for seismic inversion suitable for dense well pattern condition is explored. Through optimization of inversion parameters, the restrained probabilistic simulation method for wave impedance is optimized, the relationship among seismic inversion parameters, well numbers and sand body prediction accuracy is analyzed, the vacuated well is used for inversion test, and the predict coincidence rate of sand bodies above 3m reaches more than 85%.(3) The accuracy of predicting sand bodies between wells is risen, and the diagrams of sedimentary microfacies in Lamadian Oilfield is improved. Using inversion results of well-seismology combined seismic attributes, and combining with achievements of sedimentary microfacies under dense well patterns, the characteristics of sand body distribution are determined, and the understanding about the sedimentary microfacies are improved.(4) The morphologies of structures with micro amplitude are ascertained. Under restriction of the top and bottom surfaces and fault surface of sandstone groups that are guided by layering in wells and interpreted seismically, combining with dynamic information from well points, the error of the structural map is controlled within±2m, mostly controlling within about±lm.(5) The achievement is used in the secondary development adjustment. Using the finely structural interpretation of well-seismology combination, reservoir prediction achievements and dynamic analysis to find remaining oil enriching areas, the design of 3 horizontal wells and 4 deviated wells is finished. It can be seen from 3 horizontal wells that the penetration rate of sand body is above 70%, on the basis of prediction achievements from small faults and sand bodies, the perforation plan for new wells is optimized, the injection-production relationship of single sand body is improved, providing the further development in old oilfields with technical support.