Differentiation Characteristics Of Compaction In The Fault Zone

With the exploration of oil and gas reservoirs gradually extended from shallow layer to deep layer or ultra-abyssal layer,the study of diagenesis has gradually increased,under this trend,not only the accuracy within the reservoir diagenesis and differentiation characteristics,but also the controlling factors which caused the differentiation characteristics also increased.For the study of diagenesis,the former's study from traditional study that inorganic-organic effect of the reservoir to the study which pay attention to the basin type,tectonic deformation,burial trajectory and other dynamic factors constraints on the differentiation of diagenesis long process has completed the qualitative leap of research of diagenesis.With the deepening of the study of diagenesis,the reservoir sedimentary background,tectonic background and the external dynamic factors for the research status of diagenesis has been prominent.In the sandstone strain localization process,not only the porous sandstone reservoir compaction effect obvious difference caused by the difference of stress distribution,but also the stratigraphic discontinuity(fracture,cracks and joints)caused by strain affects the differentiation characteristics of the reservoir rock-fluid interaction.Therefore,under the strain localization background,in-depth study of diagenesis difference and its control process,and explore the main controlling factors of diagenesis difference,not only is an important complement to the understanding of Meso Cenozoic clastic reservoirs in Kuche depression evolution,but also provides a theoretical basis for the high accurate evaluation and prediction of reservoir under the fault zone pattern widely developed in China's superimposed basinsThe formation of Cretaceous Bashijiqike in Kuqa depression is the important natural gas reservoir,regardless of its efficient output performance and excellent reservoir,make it much attention.This research takes Cretaceous Bashijiqike formation third strata in the northern monoclinal zone of Kuqa depression as the main object of study,on the basis of summarizing the previous research data in sedimentary and tectonic background,stratigraphic correlation area,through field profiles and observation and measurement of group,period,size,shape,filling,cutting,density and opening of the Cracks and joints,Combined with the tectonic background and sedimentary environment,finally,established the fault pattern;According to the analysis of ore rock with the slice under microscope,observation and statistics,combined with the apparent compaction rate value which can quantitatived represent compaction,in order to identifying the temporal and spatial characteristic of the transformation into compaction diagenesis;In the calculation process of apparent compaction rate found that the content of residual primary intergranular pore determines compaction strength,therefore,we can combine with the preservation mechanism and failure mechanism of primary pore to explore compaction differentiation characteristics,research find that these control factors are: rigid particles(mainly quartz and feldspar)content,cementation strength,particle size and clay rock debris(representing plastic debris)content,finally,we use SPSS data analysis software in the multiple linear regression analysis method to identify the main controlling factors of the compaction effect differentiation characteristicsStudy on dynamics mechanism of compaction differentiation of study zone,the vertical compressive formation stress and the lateral structure pressure caused by the development of the fold belt thrust nappe fault which greatly affect the reservoir porosity and permeability.Because of the simulation of thermal evolution trajectory,the division of strata and the distribution of samples,study interval don't exist plane of unconformity,in consequence,The reservoir belongs to the same set of sand body,and the samples buried depth is basically the same,thus excluding the influence of the vertical pressure on the characteristics of the study area.The study area cracks and joints is developed,different tectonic stress in different fault pattern established,the difference in structure is largely responsible for the difference of compaction,so study reservoir compaction variation in fauylt pattern is meaningful.But the overburden pressure is an important factor that needs further research and indoor research work in large scale,study the relationship between the time distribution of the compressional stress and the control of the spatial and temporal differentiation characteristics.This study has achieved the following four important understandings:(1)According to the observation and measurement of group system,time,scale,occurrence,filling,cutting,density and open of the field section and the joint,as well as the density of cracks and the distance from the main fault,the study section is divided into strong tectonic stress zone and weak tectonic stress zone,the distribution patterns of different fault zones are established.(2)Through the statistical method of microscopic particles count,detrital composition of the target layer is statisticed,the results show that in the detrital minerals,mainly rigid particles(mainly quartz feldspar);in cements,mainly carbonate cements(mainly calcite cement),followed is clay cements;while in the reservoir space,the proportion of primary porosity is larger,and the ratio of primary porosity and secondary porosity is about 4:1,and some samples development micro fracture.According to the contents of the primary pores and cements,the characteristics of compaction differentiation were identified(3)Through the analysis of the key section C,the content of rigid particles is high,and relative content is 82.8%,it with the primary intergranular pores are positively correlated,it with apparent compaction rate are negatively correlated;The relative content of cement is 13.98%,it with primary intergranular pores are negatively correlated,it with compaction strength are positively correlated;The relative content of clay rock debris is 7.8%,and the primary intergranular pore is negatively correlated it with apparent compaction rate are positively correlated.Compared with the degree of these control factors of compaction differentiation,it is considered that the rigid particles are the main controlling factors of the compaction effect,and the second is cementation,the clay rock debris and particle size have the least influence(4)According to the characteristics of the reservoirs and the amount of interstitial matter in the study area,establishes reservoir evaluation standard in the study area,the reservoir is divided into four categories,the study area porosity mainly concentrated in the 13% to 18% range,the permeability is mainly concentrated in 5mD ~ 50 mD in summary,it belongs to medium porosity and medium permeability the reservoir,the reservoir for the class II category.