Oil recovery for fractured-vuggy carbonate reservoirs by cyclic water huff and puff: performance analysis and prediction

Abstract

Cyclic water huff and puff (CWHP) has proven to be an attractive alternative to improve oil production performance after depletion-drive recovery in fractured-vuggy carbonate reservoirs. However, due to the impact of strong heterogeneity, multiple types of fractured-vuggy medium, poor connectivity, complex flow behaviors and oil-water relationship, CWHP is merely suitable for specific types of natural fractured-vuggy medium, usually causing a great difference in actual oil-yielding effect. It remains a great challenge for accurate evaluation of CWHP adaptability and quantitative prediction of production performance in fractured-vuggy carbonate reservoir, which severely restricts the application of CWHP. For this study, we firstly enable the newly developed fuzzy grey relational analysis to quantify the adaptability of CWHP. With production history of several targeted producers, the accuracy of the proposed method is validated. Based on the traditional percolation theory and waterflood mechanisms in various types of fractured-vuggy medium, a quantitative prediction model for cyclic water cut fwp and increased recovery factor ΔR is presented. The CWHP production performance is discussed by using the Levenberg-Marquardt algorithm for history matching. With a better understanding of the fwp ~ ΔR curve characteristics in different types of fractured-vuggy medium, proper strategies or measures for potential-tapping remaining oil are provided. This methodology can also offer a good basis for engineers and geologists to develop other similar reservoirs with high efficiency.

A karst-inspired hierarchical Mg/Al layered double hydroxide with a high entropy-driven process for interception and storage

“…9–11 Nearly a half of oil and gas resources are stored in carbonate reservoirs, and many large oil and gas fields are closely related to carbonate rocks. 12,13 At the same time, groundwater is vital for supplying water and protecting biological diversity. 14…”

Influence of Water Injection Pressure and Method on Oil Recovery of Water Injection Huff and Puff in Tight Volcanic Oil Reservoirs

“…However, the following problems also exist. − (1) Although scholars have carried out physical simulation experiments of WIHP, the experimental cores used are small-sized plunger cores. For relatively homogeneous reservoirs, this is desirable, but for non-homogeneous reservoirs, small-scale cores cannot reflect the physical properties and seepage characteristics of the reservoir, and more representative full-diameter large-sized cores must be used.…”

In Situ Wettability, Capillary Pressure, and Matrix–Fracture Interactions in Fractured Oil-Wet Carbonate: A Microscale Investigation

“…Carbonate reservoirs, which exist as porous, fractured porous, and fractured vuggy systems, hold more than 60% of the global oil reserves. , Despite their considerable proven reserves, carbonate reservoirs’ primary oil recovery factor is relatively low (e.g., typically 20–35%) mainly due to their complex pore structure and predominantly hydrophobic wettability state . The recovery factor in fractured carbonate reservoirs is even lower, ranging from 6 to 8%, , due to a considerable conductivity contrast between matrix blocks and fractures. − Even with the implementation of secondary recovery processes such as waterflooding, the oil recovery from fractured carbonates cannot be substantially improved due to insignificant spontaneous imbibition of water into the oil-wet matrix. − One of the widely used techniques for enhancing oil recovery from naturally fractured reservoirs is surfactant-based chemical flooding. − Surfactants can enhance the displacement of the oil within the oil-wet matrix by reversing the wettability of the rock and/or by lowering the interfacial tension (IFT) between oil and brine. In the former case, surfactants make the rock surface less oil-wet, thereby enhancing the water intake that in turn leads to higher oil recoveries. ,− In the latter case, the reduction of the oil/brine IFT by surfactants lowers the magnitude of threshold capillary pressures of water-to-oil displacements, which also facilitates matrix–fracture interactions and hence oil production from the matrix. ,, …”

“…Carbonate reservoirs, which exist as porous, fractured porous, and fractured vuggy systems, 1 hold more than 60% of the global oil reserves. 2,3 Despite their considerable proven reserves, carbonate reservoirs' primary oil recovery factor is relatively low (e.g., typically 20−35%) mainly due to their complex pore structure and predominantly hydrophobic wettability state.…”

“…2,3 Despite their considerable proven reserves, carbonate reservoirs' primary oil recovery factor is relatively low (e.g., typically 20−35%) mainly due to their complex pore structure and predominantly hydrophobic wettability state. 4 The recovery factor in fractured carbonate reservoirs is even lower, ranging from 6 to 8%, 1,5 due to a considerable conductivity contrast between matrix blocks and fractures. 6−8 Even with the implementation of secondary recovery processes such as waterflooding, the oil recovery from fractured carbonates cannot be substantially improved due to insignificant spontaneous imbibition of water into the oil-wet matrix.…”