| The study area is an anticline which is a North West to east direction about 38 kilometers and horizontal extension of about 12 kilometers in the territory of Iraq Maysan Province.Some smaller reverse faults are generated at the bottom in the anticline.The main production zone of the target layer is the carbonate platform sedimentary environment in the Mishrif group,which is mainly based on the bio clastic limestone.The interbed/interlayer of reservoir space distributed widely,and the spatial distribution is not clear.There are interlayers at the bottom of Hartha-A,Hartha-B,Sadi A and Tanuma group as well as the top of Mishrif.In order to describe the high quality reservoir and the characteristics of interlayer distribution accurately,this paper intends to use the geostatistical inversion based on Markov chain Monte Carlo algorithm(MCMC)and the technology of pseudo acoustic curve construction,combines the results of previous studies to carry out seismic reservoir prediction research.as to put forward the favorable developed reservoir target area and the distribution characteristics of insulation interlayer.The inversion of geological statistics is a study of the parameters of the reservoir with a certain structure and random distribution in the space based on the regionalized variables,which through analysis of logging data and geological information obtained storage layer parameters of probability density function and the variogram.This method not only integrates the advantages of seismic inversion and reservoir modeling,but also makes full use of horizontal density features of seismic data and vertical density features of well logging data.In the geostatistical co simulation process,the MCMC algorithm is according to the probability distribution function(PDF)to obtain statistical significance on the sampling points.The calculation process is adJusted to achieve global optimization by means of a similar increment of the optimization algorithm(such as the change gradient method),and has the ability of fast convergence.In addition,the selection of variable range of variation function also directly affects the rate of change of reservoir parameters in a certain direction.Research shows that if the variation function variable range selected is larger than the actual data,The area / volume of the reservoir is explained to be large.This will bring a certain risk and error in the process of Wells deployment.In addition,the research area is characterized by large thickness difference and poor continuity,which are some dry layer with mainly argillaceous limestone,mudstone.The original sonic logging curve can not effectively distinguish the lithology of the reservoir,and it has brought some difficulties to the subsequent reservoir lithology classification and interpretation.To this end,the problem of lithologic impedance superposition is solved by using the quasi sonic construction technique.First of all,the log curve(natural gamma)of the target layer is found by statistical analysis;Then we should extract the original acoustic time curve which can reflect the formation background of low frequency information components by the frequency division technology and calculate the regression relationship between the natural gamma ray and the original sound wave curve with a method of statistical regression.Finally,Using information fusion technique to fuse the low frequency information of acoustic curve and natural gamma curve and constructing a pseudo acoustic curve with acoustic dimension which not only has the low frequency information which can reflect the trend of the formation change,but also can reflect the trend of the formation of the formation.The natural gamma ray curve can reflect the details of the target layer well,and the matching degree of the inversion results and the drilling has been greatly improved.Therefore,the pseudo acoustic construction technology has obvious advantages in the accurate and detailed description of the reservoir. |
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