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Description
To evaluate the gas injection potential for horizontal wells in tight oil reservoirs, a combined approach of nuclear magnetic resonance technology and gas displacement-oil physical model experiments was applied to core samples of tight oil reservoirs, investigating the distribution characteristics of crude oil in the reservoir and post-gas displacement micro-residual oil. The study revealed: before gas displacement, the target reservoir exhibited a high total oil saturation percentage, but the majority of crude oil was primarily stored in pores smaller than 1 micron, while oil saturation in pores larger than 1 micron was relatively low (7.27%). After 1 PV of gas displacement, the relative recovery (R) of crude oil in pores larger than 1 micron was high (64.34%), followed by pores in the 0.1–1 micron range (37.27%), with lower R in pores smaller than 0.1 micron. Early-stage gas displacement preferentially mobilized oil stored in larger pores, leaving smaller pores with lower oil recovery. After 50 PV of gas displacement, almost no residual oil remained in pores larger than 1 micron, with R exceeding 90%, while a certain amount of residual oil persisted in the 0.1–1 micron range (R ≈ 60%), and lower R in pores smaller than 0.1 micron, which became the primary residual oil storage space. As permeability decreased, the proportion of larger pore throats diminished, reducing micro-scale heterogeneity. Gas displacement improved micro-scale sweep efficiency, with a trend toward increased oil recovery in the 0.1–1 micron pore range. Gas injection demonstrated significantly better performance than water injection in tight oil reservoirs, and the advantage became more pronounced at lower permeability. These findings provide a basis for effective tight oil development and the formulation of appropriate development strategies.
| Country | china |
|---|---|
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