Abstract
The tight sand reservoir in Dabei Area has been the main block of exploration and development of natural gas inTarimBasin. Because of low porosity and fracture development, there exist errors in calculation of reservoir saturation. According to micro-resistivity image logging and acoustic full-wave logging, the reservoir fractural effectiveness is quantitatively evaluated; the result indicates that the reservoir with Stoneley wave permeability is greater than 0.2 × 10-3μm2; the reservoir connection is good. If the FVPA is greater than 0.055%; the fractures are developed. A new matrix saturation model is established based on the conductive pore water in consideration of the influence of low porosity. After modeling and analyzing the effect of porosity and its occurrence on the cementation index, the method for saturation calculation in Kuqa Area is established: the newly established dual porosity model is for fracture developed reservoirs, and the model based on the conductive pore water is for fracture less-developed reservoirs. By comparing the results of saturation in mercury injection experiment from coring section, precision of the calculation method is proven.
Highlights
In the tight sandstone reservoirs in deep formation of Dabei Area, permeability is poor, at the same time, as it is influenced by fractures, the curve between the deep induction resistivity and shallow induction resistivity is not very different, the fluid is impossibly identified based on the invasion characteristics
The micro-resistivity logging imaging cab be used for obtaining the intersection of apparent fractural porosity and Stoneley wave permeability; the difference between porosities calculated by density and acoustic loggings can be used for obtaining the apparent fractural porosity for evaluation
If there are no data of micro-resistivity logging, the evaluation should be carried out by using the difference between porosities calculated by density and acoustic loggings, but the result is poorer
Summary
The methods described by the above scholars have included the current technical means for identifying gas reservoirs by using logging data, in which the methods for logging identification of water zone and gas-water coexistent zone are not discussed in depth, the detecting precision and applicability of the methods for identifying the tight sandstone reservoirs remain to be verified. In allusion to the issues of deep burial, higher pressure, high temperature and hard for identification of gas and water layers in the tight sandstone gas reservoirs in Dabei Area, by using the logging data as the major means and on the basis of fine evaluation of reservoir fractures, a novel approach for calculating saturation is established in consideration of the influential factors of fractures and.
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