Research On Geophysical Reservoir Prediction Method And Application For Glutinite Bodies In Steep Slope

Petroleum exploration practice shows that glutinite body reservoirs in steep slope of rift basin were poor porosity and permeability, narrow facies distribution, and difficult to prediction. The key factor restricting the hydrocarbon exploration is to recognize and predict effective reservoirs. A case study in steep slope of northern Chezhen sag in Jiyang depression is made to deepen awareness of distribution rules of glutinite bodies in steep slope of rift basin and to approach comprehensive prediction of favorable reservoirs.Firstly, aiming at the characteristic of various deposition types, fast facies alteration and complex distribution, sequence stratigraphy research was made to approach classification plans of structure-deposition model and their characters in combination with fault styles and main deposition types and favorable facies types were made clear. Secondly, seismic prediction model for all kinds of fans of steep slope were established with forward modeling for seismic reflection wave field of various fans, and macroscopic distribution of main depositional system and favorable facies were made clear according to seismic facies features. Finally, a suit of technology and flow for reservoir prediction, hydro detection and favorable reservoir evaluation were formed based on comprehensive appliance of geophysical technology to predict favorable reservoir distribution.1. According to analysis of frontier fault styles, characters and distribution, glutinite bodies types and distribution, in combination with research about sedimentary sources property and gateway, paleoclimate and paleogeomorphology, it was made clear that frontier fault styles and distribution controlled process and scale of depositional fill, which means that glutinite bodies had developed following rules of facies controlled by fault arrangement, depositional sources controlled by structure transform zone, horizon controlled by mulriple datum plane, and reservoir controlled by microfacies. Two facies, which are nearshore subaqueous fan and deep water turbidite fan, developed in lower third member of Shahejie formation and their distribution range was made clear.2. Based on drilling, log curve and geological data analysis, dominated by seismic horizon interpretation and combined with inversion section, 2-D geological seismic model reflecting vertical multiphasic overlap and horizontal lithological alternation of different kinds of fans was made. By comparing theoretic data with practical data, rationality and validity of the model was validated. Changing of sand bodies'lithology, facies, thickness and structure will cause alternation of seismic reflection event.3. Through high-order finite difference algorithm and with the help of technology of interleaving grid, total matching strata absorbing frontier and flux transmission calibrating, high precision forward modeling using geological model for several glutinite fans of steep slope was made. Theoretic records corresponding to the real seismic data of those fans were acquired and essentially coincided with practical data. It provides foundation for further analysis of seismic reflection of fans.4. Based on difference of seismic reflection wave kinematics and dynamics of various fans, analysis about difference of reflection character in practical seismic data between individual fan was made. Models of seismic reflection character for nearshore subaqueous fan and turbidite fan in steep slope were established. Nearshore subaqueous fans distributing in steep slope of near source lake basin show weak and unstable amplitude, poor continuity, and coherence and the amplitude in middle fan is stronger and has better continuity. Turbidite fans display as sheet or small scale lens style and show strong reflection in seismic section. The reflection events of turbidite fans bifurcate and coalesce apparently. The reflection frequencies of those fans are higher and are well bedded with surrounding rock.5. With technology of well constrained poststack inversion and frequency spectrum image forming, distribution character of glutinite bodies were delineated accurately. Vertical distribution of glutinite bodies (thin alternating beds) was delineated by poststack inversion technology and areal distribution was delineated by tuning amplitude spectrum analysis of target reservoir frequency spectrum image forming. In conjunction with these two technologies, accuracy of prediction for glutinite bodies is strengthened. Nearshore subaqueous fans developed in lower third member of Shahejie formation mainly distributed in Che59 area and deep water turbidite fans mainly distributed in Che66-Che73 area.6. Based on description of glutinite bodies distribution character, prestack elastic impedance inversion, including accurate in-well S-wave inversion, distribution character of compressional and shear wave impedance and Lame's constants, was applied to analyze seismic response on different lithology, physical property and petroliferous and distribution of favorable reservoir. Prestack seismic heterogeneous fracture detecting technology, in conjunction with seismic wave forward modeling result, was applied to interpret alternation of reflection amplitude of P-wave and other seismic attribution corresponding to the change of offset and azimuth and to confirm development degree and distribution character of fractures. Based on research of favorable reservoir distribution character and according to hydro detection parameter in frequency spectrum image forming technology and Poisson's ratio parameter in prestack elastic impedance inversion technology, research about petroliferous condition in target zone of glutinite bodies reservoir was made. By these methods, it is made clear that favorable reservoirs mainly distribute in Che73 and Che66 erea.7. A suit of technology and flow for reservoir prediction, hydrocarbon detection and favorable reservoir comprehensive evaluation was formed. Aiming at geological, seismic and logging characters, high accuracy reservoir description technology was formed, especially in selection of property parameters and confirmation of distribution arrange of those parameters'value.