Upscale methodology for gas huff-n-puff process in shale oil reservoirs

Abstract

Results of recent laboratory experiment studies suggest that huff-n-puff gas injection holds great potential to increase oil recovery from shale oil cores. However, our current knowledge of the field-scale performance of this process is very limited. Reservoir simulation is required to properly upscale this process from laboratory to field conditions in order to predict oil recovery and reduce the risk of failure in field projects. After examining the literature, the purpose of all upscale methods is to generate a single curve which can describe the relationship of oil recovery versus dimensionless time for different scales. For a gas huff-npuff process applied in a shale oil reservoir, it is also necessary to generate one single type curve to upscale a lab experiment to field-scale production. In this paper a new expression of dimensionless pressure was generated to describe the huff-n-puff efficiency, and a new version of dimensionless time was also derived that includes dimensionless pressure, permeability, porosity, viscosity, and core length. A compositional numerical model with dynamic gridding was built and validated by matching the experimental data, and the model was then used to test the upscale methodology. Several validation tests were conducted for different fluid and rock parameters, well constraints, and operation schedules. To this end, a type curve was developed for different scales which demonstrates that all sizes yield a similar relationship between oil recovery and dimensionless operation time. It proves that the cumulative oil recovery of gas huff-n-puff EOR in shale oil reservoirs can be predicted. In a case of high-permeability, the curve between oil recovery and dimensionless time deviates from the type curve (moves to the right side). This indicates huff and puff times are too long, and the process is inefficient. In this case, the huff and puff times can be reduced so that the curve follows the generated type curve.

CO2, Water and N2 Injection for Enhanced Oil Recovery with Spatial Arrangement of Fractures in Tight-Oil Reservoirs Using Huff-‘n-puff

“…Cores from Eagle Ford were used in this research. Similar experiments can also be found in Li and Sheng's research [33]. The results indicated that oil recovery was improved when the soaking pressure increased.…”

A Literature Review of CO2, Natural Gas, and Water-Based Fluids for Enhanced Oil Recovery in Unconventional Reservoirs

“…Li et al at Texas Technical University compared how different gases (CO 2 , methane, and nitrogen) affect oil recovery in Wolfcamp Shale cores (Figure D) . A compositional model was built to analyze the laboratory results . The core preparation procedure shown in Figure B was used, and extractions were performed at 40 °C and 13.8 MPa.…”

“…Researchers at Texas Tech University modeled the Wolfcamp and Eagle Ford formations on laboratory-scale ,, and field-scale. ,,,,, After 10 years of primary production and 60 years of continuous gas injection from separate vertical injection and production wells, 15% oil recovery resulted from the low-permeability homogeneous medium (Table , entry 6) . These results were superior to primary production alone (6.5% recovery) or primary production followed by waterflooding (12%).…”

“…Li et al modeled laboratory-scale methane huff-n-puff laboratory experiments and scaled results for methane huff-n-puff field cases (Table , entries 12 to 14). , They found that increasing the injection time improved oil recovery because it increased the average pressure and miscibility. Further, they recommended reducing the pressure as much as possible during the puff cycle.…”

A Review of Gas Injection in Shale Reservoirs: Enhanced Oil/Gas Recovery Approaches and Greenhouse Gas Control

“…Water floods, commonly being used in conventional reservoirs as an improved oil recovery (IOR) method, has been proven to be unfeasible in tight unconventional shale formations [17,27]. In the past decade, gas injection, including huff-n-puff injection or cyclic gas injection, and gas flooding, has been demonstrated to be a promising EOR method for shale reservoirs and has been extensively studied in oil and gas research laboratories and widely modeled through numerical simulation methods by many researchers [8][9][10][11][12]14,16,17]. We review the recent research progress on gas injection in shale oil reservoirs through huff-n-puff (Section 2.1.1) and gas flooding (Section 2.1.2) methods and summarize the gas injection mechanisms in Section 2.1.3.…”