Experimental investigation of a low-molecular-weight polymer coating agent for deep-sea oil and gas drilling

Abstract

In order to solve the problems due to the thickening of drilling fluids at low temperatures caused by the use of high-molecular-weight polymer coating agents in offshore deep-sea oil and gas drilling, a low-molecular-weight polymer coating agent named PADA was synthesized with acrylamide, methacryloxyethyltrimethyl ammonium chloride, and 2-acrylamido-2-methyl propane sulfonic acid. The PADA polymer was characterized with Fourier transform infrared spectroscopy and gel permeation chromatography. The shale inhibition effects of the PADA polymer and associated mechanisms were investigated by shale recovery and expansion experiments, transmission electron microscopy observation, particle size and zeta potential analysis, and interlayer spacing measurements. In addition, the effects of the coating agent on the filter cakes and the low temperature rheological properties of bentonite mud were also tested, and the polymer biodegradability was evaluated. The results showed that the molecular weight of the PADA polymer was 265,000 D, which was significantly lower than that of the traditional coating agents. The PADA had similar effects as two typical commercial products CAP and HPAM on inhibiting the hydration dispersion of shales and performed better than another product PAM. The inhibition effect was achieved by the polymer absorption onto the clay particles through both hydrogen bonding and the electrostatic interactions. The viscosity of bentonite mud containing PADA was much lower than that of mud with other coating agents at 4 °C, so the serious thickening caused by traditional coating agents at a low temperature could be avoided. In addition, it is relatively easily biodegraded.

Synthesis and Characterization of a Cationic Micro-crosslinking Polymer and its Application as a Fluid Loss Reducer in Water-based Drilling Fluids

“…Coupled with the complex geology of deepwater shallow formations, this exacerbates the instability of shallow formations and places more stringent requirements on the wellbore stability performance of drilling fluids [5] . In response to the strict wellbore stability requirements under the narrow safety density window, many high performance deepwater water-based drilling fluids have been developed, among which filter loss reducers as the core treatment agents of high performance drilling fluid systems have been intensively studied [6] . ULTRADRILL drilling fluid is a high-performance deepwater water-based drilling fluid system introduced by Schlumberger MI SWACO, and the core material was developed by Arvind Patel et al [7] .…”