The Study And Comprehensive Evaluation On The Parameters Of Tight Sandstone Reservoir With Well-logging Method

With the oil exploited in depth, low porosity and permeation sandstone reservoir have get more attention. But it is difficult to evaluate it with well log data. How to evaluate and describe the reservoir are the most important, when we evaluate the low porosity and permeation sandstone reservoir. There are many different properties between the low porosity and permeation sandstone reservoir and common reservoir. Because of the features of the low porosity and permeation, the fluids in the reservoir make less contributions to the responsiveness of the log, besides existing the influence of the well borehole and other conditions. In addition, they make part of log well information lack fidelity. Above all,it is very difficult to distinguish and evaluate the fluid in the low porosity and permeation reservoir.By the study of the tight sandstone reservoirs around the world, we can sum up it include the following characteristics:tight lithology、low porosity and permeation、low capacity、low pressure modulus and so on. As a result of the compaction effect, there are some fracture developed and vertical and lateral heterogeneity characteristics in different tectonic belt.Sulige gas field is the biggest one in our country. In this area,there are so many tight sandstone reservoirs that it has a good prospect for development. As the result of the tight lithology and serious compaction,the reservoir has bad pore-throat connection、high capillary pressure and low porosity and permeation.there are many fracture, that made the pore structure complex, developed in different layers. Base on those reasons, there are many differences between the tight sandstone reservior and common reservoirs when we do the evaluation. How could we effectively and exactly evaluate the characteristics:low porosity、low permeation、low capacity、abundance and the tiny fracture of the reservoir is the puzzle when we are developing and exploring the reservoir of the Sulige. The issue of the paper have brought up in this background, in order to find easy and effective new ways to evaluate the reservoir by the studies. At last we can do assistance for low porosity and permeation evaluation in this area when exploring.In this paper, we try to find new ways to evaluate the low porosity and permeation reservoir using the well log data、core and test informations when we make the study of the reservoir. Besides, we attempt to study the pore structure、calculate the capacity and evaluate the permeation for the low porosity and permeation reservoir, then get part of progress. In study of the geological feature and the physic characteristic, we realized the main lithologies of the area including:siltstone、fine-grained sandstone、medium sandstone、coarsest sandstone and pebbled sandstone. And the pore is3-12%、 permeation is0.01-2.3mD, radius of pore and throat is less than0.1mm. It based the foundation of the synthetical evaluation of the tight sandstone reservoir by the study of the geological feature and the physical characteristics. On the study of the pore structure, we used the fractal feature of the NMR to show the pore character,and analysised the relationship between the fractal dimension feature and the physical property. By the study of the fractal dimension feature in depth, we have get the fractal feature long the depth, and used the relationship between NMR fractal and well-log data fractal to show and evaluate the reservoir characters. On study of the core imformations and well-log data,we have learn that:the lithology property is the base, and it control physical property which handled the oily and electrical properties. Based on the above, we have established the well-log evaluation model. Making full use of the conventional and imaging well log informations to distinguish the fracture. It is proposed that using the characteristics of differential normal well-log to identify the fracture, besides using the resistivity in deep and shallow to evaluate the parameters of the fracture. We have established the BP neural network model,which used for forecast the capacity,based on the pore、permeability and the layer thickness We adopt those ways:double porosity overlap、natural gas mark and layer framework density to distinguish gas layer. In those methods double porosity overlap and natural gas mark do it well in the progress of gas layer distinguish.