| Fractured reservoir logging evaluation, the frontier subject of well logging, has always been a serious problem in log interpretation. The key is identification and quantitative evaluation of crackBorehole face imaging logging(FMI,EMI,STAR-Ⅱ) can provide borehole wall formation image with high resolution. We can directly identify reservoir characteristics such as cracks and holes. At present it has been widely used in the recognition and evaluation of the complex fracture-vuggy type reservoir like carbonate rock and volcanic rock. In recent years at home and abroad some oil fields have done creative work in the fracture identification and quantitative evaluation (mainly in effective crack) and related applications. Achievements has been widely used in production. But compared with fracture filling properties and quantitative evaluation, the focus of the study is on the cracks open effectiveness.Filling characteristics and the issues of crack and karst cave are directly related, as well as ancient tectonic movement and palaeostress field. And ancient tectonic movement and palaeostress field decide the extension azimuth of fracture and other important parameters.At the same time imaging logging has certain response to the filling characteristic of karst cave and cracks.Research on the subject has the vital significance on looking for fractured reservoir and the exploration and development of oil field.Based on detailed observations of the core and the analysis on crack, types and characteristics of karst cave of the area, the fissures of the area are structural fractures, dissolution fractures, filling cracks and open fissure (half filling and no filling). Fracture fillings are mainly clay, pyrite and calcite. After depth migration and contrast with imaging logging data and conventional log data, summarizing the different filling fracture imaging logging and conventional logging response characteristics, process the imaging logging data of the area, analysis the different layers in the region of different types of fracture law of vertical and horizontal.Combining with regional geological regularity and stratigraphic evolution history, dividing the filling fracture and cavity through issues, and summarizing the characteristics of logging response of fractures in different periods. According to the processing results of imaging logging, and then explore the relationship between ancient cracks, the karst cave in each issues,the filled fracture and palaeostress field; At last according to the principle of rock mechanics and geomechanics study the methods to explore the current stress field and palaeostress field.In order to study the palaeostress field, rock mechanics parameters experiments are conducted. Based on the analysis of the experimental data of rock mechanics, dynamic and static conversion model of the rock mechanics parameters in the research area and calculation methods are proposed. Processing the rock mechanics parameters and the principal stress magnitude as well as direction and then summarizing the Ordovician strata of rock mechanics characteristics and change laws. To explore the present stress field characteristics and change rules, and according to the characteristics of filled fracture (filling type, direction, fillings) and filled fracture issue, combined with the ancient geographical law of motion and the geological, seismic research and the personnel experience of the area, we can explore the characteristics of the palaeostress field and the change rule.The following achievements are obtained by the research:1) The cracks of the research area include structural fractures dissolution fissure, filling cracks and open fracture (half filling and no filling), type of fracture fillings are mainly argillaceous, calcite and pyrite (mainly argillaceous filling, followed by calcite filling). Crack occurrence are mainly vertical, diagonal and horizontal. In the development of the cracks, filling seam for78.6%, half filling and no filling for only14.9%and9.9%. Crack width is most in from0-1mm to1-2mm.2) Different types of cracks on the electric imaging logging have different response:Generally, argillaceous filling and pyrite filling cracks on the images show the dark high conductivity characteristics, similar to no filling crack. While calcite (calcite vein) filling cracks have a white high resistance characteristics.3) The ancient crack in research area roughly made up of four different tectonic movement in different periods, the cracks in addition to the early diagenetic formation are roughly divided into four periods:the early diagenesis, late caledonian to early hercynian, late hercynianindosinian period, yanshan and Himalayan period, it shows that the distribution of fracture development degree is mainly controlled by tectonic action.4)The ordovician carbonate formation of the reaearch area contains both unfilled caves and filled ones, and the manifestations of the caves are complex and diverse. The scale of unfilled caves whose diameter is on the level of millimetre to centimetre are small, while the diameter of filled ones fluctuates from millimetre to meter. Most of the large caves are filled. The ingredients of filled caves change significantly, which mainly are argillaceous or arenaceouspelitic sediments, karst breccia and miarolitic or layered carbonate rocks which are related to chemical precipitation of the cavern water. In the form of caves, there are mainly four basic types---mottled-patchy small and medium sized cave, flaky fracture cave, mesh fracture cave and layered large cave.5)The Ordovician cracks and solution cave are mutually associated in the area. Solution cave is developed in the fissure strata and different types of caves can be formed by the erosion of different types of fissures. Single crack can develop the beadlike caves by erosion along the fracture surface; more cracks’cross development can form layered caverns by corrosion expansion. Near the fracture zone, especially the Multiple sets of fault zone, often can form better reservoir with both fissures and caves. The schistose cave can be easily formed by the first phase’s fractures through corrosion. The second phase of the conjugate shear joints can form caves while The third crack can easily develop string of beads shaped caves by the corrosion.6)Elasticity modulus, Shear modulus and bulk modulus of the study area on the whole range is not big, respectively is14.23～29.563GPa,5.759～12.483GPa,13.278～23.008GPa; Three modules in the longitudinal from the Liang one to the Liang four section increased in turn, but it becomes smaller in the Liang two section which is different in the whole change tendency; The shear strength from the Liang one to the Liang four section reduced in turn, but the shearing strength on the whole range is not big and the regularity is not obvious; Because the core sample is limestone, the Poisson’s ratio changes not in a big way in the value, its value appears in0.247～0.361scope; From the Liang one to the Liang four section, the Poisson’s ratio has a small tendency on the whole, but appears the maximum value in the Liang three section; With a well rock mechanics parameters shows obvious heterogeneity and anisotropy, which reflects work area formation anisotropy 7) According to the issue of old fracture and the analysis of the current stress field, the change of ancient stress field in wellblock are as follows:the first phase of the cracks are tiny seam, argillaceous filling is irregular, more common cutting phenomenon. Squeezing action of the Kunlun Mountain terrane and transit body corresponding second stage fracture by tectonic movements, mainly resulting NEE-SWW to Zhang shear fractures which indicates the direction of the ancient stress; Phase three crack affected by the south tianshan mountain to the south thrust action, fracture trend shows that the issue of stress is NNW-SSE direction; Fourth crack due to the complexity of the Tarim block was first constructed extrusion process after stretching, due to compression asymmetry, spin regional stress field was formed, the ancient stress direction which fracture reflects is NNE-SSW direction, shear mechanical properties of the cracks at the same time also verified the right-lateral stress field. |
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