Changes in formation pressure and technological efficiency of unsteady flooding in double permeability reservoirs having different productivity rates

Abstract

Unsteady waterflooding went through several stages. Within the pilot works in April 2009, cyclical water injection was started in Block 7 (central section). In addition, alternate water injection into the horizons of the Jurassic and Cretaceous sediments of Block 10 began. For this purpose, injection wells equipped with devices for simultaneous separate water pumping were used. The significant effect of non-stationary waterflooding in the experimental sections allowed for the application of the technology in other blocks. The technology implementation scheme was applied for injection wells of Blocks 6 and 10. Since July 2010, cyclic injection has been used for many wells. Periods of non-stationary operation of injection wells were determined experimentally. The reservoirs with heterogenous permeability containing highly permeable and low-permeable layers are the most optimal ones. The heterogenous structure of the reservoir provides a large contact area between layers with different permeability levels which allows for non-stationary effects due to the occurrence of overflows between the layers. It can reduce the water content of the products and increase oil production.

Impact of hydraulic fracturing on the creation of highly permeable channels within the Earth’s interior

“…It is the most developed (at the moment, the production of recoverable reserves makes 78.8%, the share of remaining recoverable reserves in the total volume has decreased from 90.7% to 75.6%). Differences in the degree of their production are primarily determined by different commissioning periods [1,5,10].…”

“…As a rule, reservoirs with low permeability are mainly characterized by a pronounced macroinhomogeneity of reservoir properties both in height and in formation direction. In this case, the purpose of hydraulic fracturing is to increase the productivity of wells by impacting on the bottomhole zone of a well -a change in the properties of the porous medium and fluid (the properties of the porous medium change during hydraulic fracturing due to the formation of a crack system) [1,3,7].…”