Log Cycle Analysis And Reservoir Prediction Of Fluvial Deposition In Zhuang106Block In Laohekou Oilfield

As the old area in Shengli Oilfield has entered the end of the stable production period, the structural reservoirs that are morphologically relatively simple and easy to find have been basically discovered, so exploration work are gradually turning to miniature hidden oil and gas reservoirs which are tectonically relatively complex and change rapidly vertically and horizontally, such as beach-bar sandstone body, fluvial sand bodies and so on. The upper member of guantao formation in the Zhuang106block in the Laohekou oilfield consists of fluvial deposits. Generally speaking, fluvial sand layers are relatively thin, and thin sand layers and thin mud layers often compose thin Interbed, which make it difficult to identify the sand layers by using seismic data. Fluvial sand body changes little and extend by a certain length along the river, however, it changes rapidly perpendicular to the river, and, in the geological history, river channel change continually, and river in later period might erode deposition of that in early period, and depositions of multi-phase rivers may overlay,which result in that connectivity relationship between sand bodies is very complex, and greatly reduce the reliability of correlation of reservoirs at the same layer among the adjacent wells, and lead to effect of water injection is not good in the development eventually. The main purpose of this paper is to study the corresponding solution for the problem above, the research include the following points:(1) Through Analysing the existing geological, seismic, drilling and logging data, the paper learn corresponding relationship between the various types of well logs and lithology, and selects GR log as mastery log,which is the most sensitive to lithology;(2) Considering INPEFA curve calculated from the original well log by spectral trend attribute analysis method reflects the cycle information more clearly than the original log, the paper calculates INPEFA curve from GR log,which is used for formation cycle correlation in Zhuang106block; (3) With the help of geological, logging, drilling and seismic data, the paper does fine structure interpretation of three-dimensional seismic data to build up seismic sequence stratigraphic framework, and correlate sand group-level cycle by INPEFA curve at the same time to build up drilling(logging) sequence stratigraphic framework, and check the two sequence stratigraphic frameworks through comparing them to build up the comprehensive sequence stratigraphic framework in the area eventually;(4) Under the control of the comprehensive sequence stratigraphic framework,the paper identifies and tracks reflection axis of the fluvial deposition with the help of amplitude slice and coherent body slice, and correlate fluvial deposition cycle by INPEFA curve at the same time, and the two aspects cooperate each other,and check up each other to ensure that tracking and correlation of the fluvial deposition are reasonable.(5) In order to identify thin layer of sand and finely characterize sand body, the paper applies logging constrained sparse spike inversion method to obtain acoustic impedance data. As reservoir in the upper member of guantao formation in the area is shallow and uncompacted, and acoustic logging was affected by borehole environment and logging cycle, the sonic log data can not correctly reflect the difference in speed between the different lithologies,and can not be used for inversion.Through analyzing the ability of a variety of well logs to identify the lithologies, the paper finally choose COND log to reconstruct "pseudo-sonic" log,which is contrasted with core data to prove that the "pseudo-acoustic" log can correctly reflect the speed difference between the different lithologies;(6) The paper evaluates the result of logging constrained sparse spike inversion from six aspects, which shows that the credibility of the inversion result is high, and the difference between large impedance value and small impedance value is obvious, and geological phenomenon is clear,and the resolution is relatively higher,and the inversion result can accurately reflect the actual underground geological conditions, so the result can be used for the following reservoir analysis and research;(7) The paper use the method of analysing seismic data and acoustic impedance data simultaneously to contrast the two in both2-D section and3-D space with reference to a variety of well logs and INPEFA curve to track and interpret the sand bodies, which has a good effect;(8) Under the control of drilling, logging data and results of well log interpretation, the paper draws the map of top surface structure and thickness of the sand bodies that have been tracked and interpreted.The above research has some effect on solving the problem that correlation of fluvial sedimentary strata is difficult, and connectivity relationship of sand bodies is ambiguous in the area, providing some guidance and reference for fluvial reservoir exploration and development in the future.