Journal of Petroleum Exploration and Production Technology最新文献

Abstract

The interlayer can effectively prevent the ridge of bottom water and has a non-negligible influence on the flow dynamics of oil and gas in the reservoir. In view of the above problems, this paper studies the influence of a bottom water reservoir with an interlayer on the critical productivity of horizontal wells and establishes a coupling model of seepage and wellbore flow in a bottom water reservoir with an interlayer. The critical productivity of horizontal wells in a bottom water reservoir with an interlayer can be evaluated more accurately. Firstly, the three-dimensional seepage field is approximately decomposed into internal and external seepage fields, and the critical productivity formulas of internal and external seepage fields are solved, respectively. Using the equivalent seepage resistance, the critical productivity formula of horizontal wells in interlayer bottom water reservoirs is obtained. The results are compared with the calculation results of the traditional productivity formula and the simulation results of the commercial software ECLIPSE. Second, based on the mass conservation principle and momentum conservation principle, the wellbore-reservoir coupling mathematical model of a horizontal well is established by the discrete method. Finally, the sensitivity analysis of the selected parameters is discussed in detail. The results show that: (1) compared with the traditional productivity algorithm, the algorithm considers the influence of interlayers on productivity and gives a detailed theory, a specific calculation process, and the importance of accurate prediction of wellbore flow. (2) The model is calculated by an example, and the calculation results are compared with the traditional formula and the commercial simulator ECLIPSE. The results show that the horizontal well productivity formula considering the influence of interlayer is closer to the simulation results of commercial software ECLIPSE, and the relative error is 8.56%. (3) The established coupling model considers the influence of interlayer radius length and horizontal well length. The general trend is that productivity gradually increases with an increase in interlayer radius length or horizontal well length, but the growth rate gradually decreases.

Bentonite suspension in water-based drilling fluid is susceptible to deterioration in high-temperature environments, hence requiring a deflocculant to stabilize the solid particles. Considering the use of highly toxic chrome-based deflocculant in the industry, Rhizophora spp. tannin-lignosulfonate (RTLS) was synthesized in this study as an alternative deflocculant. A viscometer was used to study the rheological properties, and the filtration performance was evaluated using low-pressure low-temperature and high-pressure high-temperature filter press in accordance with the American Petroleum Institute standard procedure. The addition of 0.5 wt% RTLS to water-based drilling fluid (WBDF) was effective in a significant reduction of the plastic viscosity (PV) and yield point (YP) of WBDF at elevated temperatures. As the amount of RTLS added to the suspension exceeds 0.5 wt%, the effect on PV and YP becomes negligible. A higher fluid loss of 13 mL was observed in the WBDF without RTLS aged at 177 °C. The addition of 2.0 wt% RTLS reduced the fluid loss to 10.7 mL. This suggests that RTLS is an effective deflocculant that can be used to improve the filtration properties of WBDF at high temperatures. The morphology of RTLS filter cakes was examined using field emission scanning electron microscopy with energy-dispersive X-ray spectroscopy (FESEM-EDX). The interlayer between clay particles was identified as RTLS, a natural additive that plays a vital role in enhancing filtration while minimizing fluid loss. The outcomes of this research are promising, and this non-toxic deflocculant has the potential to replace chrome-based deflocculants that are still in use for borehole drilling.

Abstract

This paper highlights the efficacy of the finite element method with embedded strong discontinuities in modeling discontinuities in porous media, specifically in the geomechanical behavior of Naturally Fractured Reservoirs (NFRs). The approach considers hydromechanical coupling and offers low computational cost. NFRs account for a significant portion of global reserves, representing approximately 60% of global oil reserves and 40% of gas reserves. Given that flow in NFRs is more complex than in conventional reservoirs due to the presence of multiple fractures, it's crucial to understand how pressure variations or effective stress during operations impact fracture closure and permeability of these reservoirs. To analyze this behavior, numerical simulation results using the proposed method were compared, under different liquid pressure depletion values, with the approach proposed by Oda, which is commonly used in commercial software for calculating fracture permeability tensors. This approach was enriched with Barton's fracture closure formulation and updates on rock matrix porosity and permeability. Four simulations were conducted: Firstly, a hypothetical scenario consistent with Oda's assumptions, where fractures are interconnected and span the entire grid cell, to validate the numerical hydromechanical model; subsequently, three representative sections of a Brazilian pre-salt carbonate reservoir were selected. The study confirms the efficacy of the technique of embedded strong discontinuities in calculating equivalent permeabilities in NFRs, considering geomechanical effects, especially in cells with high fracture frequencies and intensities. Furthermore, the relevance of analyzing the geomechanical behavior in NFRs is emphasized.