Abstract
Stress sensitivity is a key factor affecting the productivity of single wells in low permeability gas reservoirs. A well test model for heterogeneous composite gas reservoirs under the influence of stress-sensitive effects was established. Based on the theoretical model, the well test was designed by gradually increasing the pressure difference. The relationship between abnormal high pressure and reservoir stress sensitivity was analyzed. Theoretical research shows that stress sensitivity will cause permeability damage during the production process, and the pressure drop test curve shows that the physical properties of the reservoir have gradually deteriorated. The pressure recovery test curve shows that the physical properties of the reservoir are getting better. Field practice shows that stress sensitivity is related to the formation of abnormally high pressure in the formation without considering the micro-cracks in the formation. Stress-sensitive reservoirs are generally unbalanced and compacted due to overpressure, for fluid expansion/conduction overpressure in Ledong Area. For these reservoirs, there is almost no stress sensitivity. The research results have significance for guiding the design and data interpretation of stress-sensitive reservoir.
Highlights
Stress sensitivity is a key factor affecting the productivity of single wells in low permeability gas reservoirs
Theoretical research shows that stress sensitivity will cause permeability damage during the production process, and the pressure drop test curve shows that the physical properties of the reservoir have gradually deteriorated
Considering the reservoir stress sensitivity has a significant impact on the development, a reasonable test scheme is designed for the exploration wells in the exploration stage, and the well test data are tried to be used for interpretation and acquisition Stress sensitive parameters
Summary
In view of the development of an ultra-high pressure gas reservoir, the stress sensitivity of the reservoir is the most discussed in China [1] [2] [3] [4] [5]. Due to overpressure in the initial stage of the ultra-high pressure gas reservoir, the net effective overburden pressure of the rock skeleton is much higher than that of a conventional gas reservoir in the depletion production process, so it is generally considered that the stress sensitivity is stronger [6] [7]. There is no report on well test model of heterogeneous composite gas reservoir considering stress sensitivity [8] [9] [10] [11] [12]. Based on the unsteady flow theory of gas well, the well test model of heterogeneous composite gas reservoir considering stress-sensitive effect is established by using Laplace transforms and perturbation transformation principle. The model is used to interpret the well test data of exploration wells, and the influence of different overpressure causes on reservoir stress sensitivity is discussed [13] [14]
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