Performance of Oil-Based Cement Slurry as a Selective Water-Plugging Agent in High-Temperature and High-Salinity Cave-Fractured Carbonate Reservoirs

Abstract

Excessive water production has been one of the most pressing issues facing oilfields worldwide. The low-level success rate caused by complicated well and reservoir conditions drives the development of an effective selective blocking agent that is suited to a simple plugging technique. In this study, we present a novel selective blocking agent that is oil-based cement slurry (OBCS) mainly composed of 0#diesel, crude oil, class G oil well cement, silica fume, a wetting and dispersing agent (sodium alcohol ether sulfate (AES)), and a retarder GH-9 (a copolymer of 2-acrylamido-2-methyl propane sulfonic acid and itaconic acid). The effectiveness of AES and the compatibility of AES and GH-9 when coexisting in the suspension system were investigated by microscopic experiments. The hydrated phases of the OBCS at 130 °C and high salinity (210 000 ppm) formation water were analyzed by X-ray powder diffraction (XRD). Thermogravimetry/differential scanning calorimetry (TG/DSC) was employed to study the products and content (mainly calcium hydroxide (CH)). The water-plugging performance of the OBCS was studied by carrying out core physical simulation experiments. XRD analysis reveals the presence of CH, calcium silicate hydrate (two types, Ca2SiO4H2O and Ca6Si3O12H2O), ettringite, killalaite, and Xonotlite. Although TG/DSC analysis fails to calculate the content of CH as expected, it gives an indication that oil exists in the set cement. The results of the microscopic experiments show a good effectiveness of AES and compatibility of AES and GH-9. High-quality plugging performances were observed in core physical simulation experiments. The properties tested indicate that the OBCS is a promising prospect as a selective blocking agent for water treatment in high-temperature and high-salinity cave-fractured carbonate reservoirs.

Mechanically robust re-crosslinkable polymeric hydrogels for water management of void space conduits containing reservoirs

“…Comparison of mechanical strength of the particle gel re-formed in NaCl and CaCl 2 solution. The bulk gel was formed by addition of sample 2 of 1 g in 1 wt% NaCl and CaCl 2 of 20 mL upon standing at room temperature for 12 h. High salinity of Ordovician cave-fractured carbonate reservoir such as Tahe oilfield hadan adverse effect on PPG, which dramatically reduce swelling ratio and stability of the gels [28,29]. Salt tolerance of the re-formed particle gel was examined under different salt solutions.…”

Synthesis and property evaluation of a novel polyacrylamide‐montmorillonite composite for water shutoff and profile control in high salinity reservoirs

“…Figure shows the schematic of core physical simulation experiments. The fractured cores used in these experiments were prepared as described in our previous study . All the cores used were standard cores with the diameter of 2.5 cm and length of 7.0 cm.…”

Research on water invasion performance of complex fracture-vuggy gas reservoirs based on classification modeling

“…The development degree of low angle oblique fractures is weak, and the fracture strike is mainly in the NWW direction (Fig. 5) (Yuan et al, 2014).…”

“…Dynamic research on triple-medium carbonate reservoir water invasion, among other methods, is often based on experiments and core analyses. Many scholars have constructed physical models of vugs and fractures through experiments to characterize the influence of triple media on water invasion; some researchers even analyzed the cores of different types of reservoirs and the influence of water invasion in terms of phase permeability (Yuan et al, 2014;Ni et al, 2016;Li et al 2019;Wang et al, 2019a).…”