Improving the Weak Gel Structure of an Oil-Based Drilling Fluid by Using a Polyamide Wax

Abstract

Oil-based drilling fluids (OBDFs) are widely used, but there are common problems associated with them, such as low yield point and poor cutting–carrying and hole cleaning ability. In this paper, a polyamide wax (TQ-1) was synthesized from dimeric acid and 1,6-hexanediamine to improve the weak gel structure of OBDFs. The TQ-1 was characterized by Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). Then the effect of the TQ-1 on the stability of the water-in-oil emulsion was studied by sedimentation observation, stability analysis, an electrical stability test, and particle size measurement. The effect of the TQ-1 on the rheological properties of the water-in-oil emulsion was analyzed by viscosity vs. shear rate test and the three-interval thixotropic test. Finally, the performance of the TQ-1 in OBDFs was comprehensively evaluated. The experimental results showed that the initial thermal decomposition temperature of the TQ-1 was 195 °C, indicating that the TQ-1 had good thermal stability. After adding the TQ-1, the emulsion became more stable since the emulsion stability index (TSI) value decreased when the emulsions were placed for a period of time and the demulsification voltage was increased. The TQ-1 could form a weak gel structure in the water-in-oil emulsions, which made the emulsions show excellent shear thinning and thixotropy. TQ-1 can improve the demulsification voltage of OBDFs, greatly improve the yield point and gel strength, and largely reduce the sedimentation factor (SF). In addition, TQ-1 has good compatibility with OBDFs, and in our study the high-temperature and high-pressure (HTHP) filtration decreased slightly after adding the TQ-1. According to theoretical analysis, the mechanism of TQ-1 of improving the weak gel structure of OBDFs is that the polar amide group can form a spatial network structure in nonpolar solvents through hydrogen bonding.

Application and Research Prospect of Functional Polymer Gels in Oil and Gas Drilling and Development Engineering

“…Weak gels are three-dimensional crosslinked systems consisting primarily of inter-and intramolecular crosslinkers, complemented by low concentrations of polymers and weak crosslinkers. As the concentration of crosslinkers increases, the network structure of the weak gel becomes more uniform and stronger (Huang et al [66]). The formation of weak gels with a spatial network structure by hydrogen bonding of polar amide groups in nonpolar solvents can make the emulsions exhibit excellent shear thinning and thixotropy, which substantially improves the gel strength and solves the problems of low yield point, rock carrying and poor borehole cleaning ability.…”

Development of Multiple Crosslinked Polymers and Its Application in Synthetic-Based Drilling Fluids

“…The synergistic effect of covalent micro-crosslinking enabled the DF to have excellent rheological and filtration properties even at 200 • C, which greatly improved the operational stability of the DF. Huang et al [17] synthesized a polyamide wax (TQ-1), which formed a weakly crosslinked gel structure in OBDF by hydrogen-bonded crosslinked. It was shown that TQ-1 could increase the ES values of OBDF, greatly improve the yield point and gel strength, and greatly reduce the sedimentation factor (SF).…”

Evaluation of Supramolecular Gel Properties and Its Application in Drilling Fluid Plugging

“…Unlike traditional covalently bonded high molecular gels, supramolecular gels are mainly self-assembled by non-covalent bond interactions, which have reversible structure and high performance [29]. At present, the problem of good leakage has become particularly prominent, especially the problem of malignant leakage in complex drilling engineering [30,31]. The conventional hydrogel used for plugging has achieved good results in dealing with small and medium fractures and leakage of permeable drilling fluid.…”