Simulation Study of Allied In-Situ Injection and Production for Enhancing Shale Oil Recovery and CO2 Emission Control

Abstract

The global greenhouse effect makes carbon dioxide (CO2) emission reduction an important task for the world, however, CO2 can be used as injected fluid to develop shale oil reservoirs. Conventional water injection and gas injection methods cannot achieve desired development results for shale oil reservoirs. Poor injection capacity exists in water injection development, while the time of gas breakthrough is early and gas channeling is serious for gas injection development. These problems will lead to insufficient formation energy supplement, rapid energy depletion, and low ultimate recovery. Gas injection huff and puff (huff-n-puff), as another improved method, is applied to develop shale oil reservoirs. However, the shortcomings of huff-n-puff are the low sweep efficiency and poor performance for the late development of oilfields. Therefore, this paper adopts firstly the method of Allied In-Situ Injection and Production (AIIP) combined with CO2 huff-n-puff to develop shale oil reservoirs. Based on the data of Shengli Oilfield, a dual-porosity and dual-permeability model in reservoir-scale is established. Compared with traditional CO2 huff-n-puff and depletion method, the cumulative oil production of AIIP combined with CO2 huff-n-puff increases by 13,077 and 17,450 m3 respectively, indicating that this method has a good application prospect. Sensitivity analyses are further conducted, including injection volume, injection rate, soaking time, fracture half-length, and fracture spacing. The results indicate that injection volume, not injection rate, is the important factor affecting the performance. With the increment of fracture half-length and the decrement of fracture spacing, the cumulative oil production of the single well increases, but the incremental rate slows down gradually. With the increment of soaking time, cumulative oil production increases first and then decreases. These parameters have a relatively suitable value, which makes the performance better. This new method can not only enhance shale oil recovery, but also can be used for CO2 emission control.

Synergistic Modes and Enhanced Oil Recovery Mechanism of CO2 Synergistic Huff and Puff

“…Several CO 2 huff-and-puff field practices at home and abroad, comprehensive analysis results of implementation plans, and development effects of CO 2 huff-and-puff field applications in heavy oil and fault-block reservoirs have indicated that wells in the lower structural position show better performance in CO 2 huff and puff. Moreover, for the fault-block reservoir, the limitation of horizontal well arrangement along the direction of structural rise is identified as three rows [40,41]. We have calculated the development conditions of the CO 2 synergistic huff-and-puff well group, which include the number of synergistic huffand-puff wells, structural position of synergistic wells, positional relationship between the synergistic wells' ligature and structural contour, synergistic well spacing, CO 2 injection volume, and type of well pattern.…”

Experimental Investigation on the Characteristic Mobilization and Remaining Oil Distribution under CO2 Huff-n-Puff of Chang 7 Continental Shale Oil

“…[16] used the molecular dynamics simulation method to find that supercritical CO 2 can affect shale oil in both inorganic and organic nanopores, but water only works in inorganic nanopores. H. Yu [17] found that CO 2 huff-n-puff could more effectively improve oil recovery for shale with an ultra-low permeability through the numerical simulation method. Gamadi and Li L. et al [18,19] used a component simulator to analyze the effects of reservoir heterogeneity, soaking time, injection pressure, and huff-n-puff cycles on EOR.…”