Investigation of ammonium–lauric salt as shale swelling inhibitor and a mechanism study

Jie Zhang,Tiehu Li,Gang Chen,Dan Cai,Li Zhang,Weimin Hu

doi:10.1177/0263617418809832

Abstract

In this work, a series of ammonium–lauric salts (ALS) was prepared with lauric acid and amines as small molecular shale swelling inhibitor. The inhibitors were screened by the linear expansion test first, and the result shows that the inhibitor prepared by lauric acid and diethylenetriamine with the mole ratio of 2:1 (ALS-2) displays excellent inhibition effect on the hydration expansion of bentonite. The inhibition of ALS-2 to bentonite was fully evaluated by various methods in the following work, including clay linear swelling test and particle distribution measurement. The results show that ALS-2 has superior performance to inhibit the hydration swelling and dispersion of bentonite, and the swelling rate of bentonite in 0.5% ALS-2 was reduced to 29.7%. In water-based drilling fluid, ALS-2 is compatible with the conventional additives, and it can improve the lubricity of the mud cake obviously after aged under 120°C. Besides, it can control the particle size of bentonite in water. The inhibition mechanism of the ammonium–lauric salts was discussed in detail through physical adsorption, scanning electron microscopy, X-ray diffraction, thermogravimetric analysis, and Fourier transform infrared spectroscopy.

Highlights

The shale oil/gas exploration is developing rapidly in recent years
The results indicate that ammonium–lauric salts (ALS)-2 can inhibit the swelling and dispersion of bentonite, and an excess of ALS can result in flocculation due to electrostatic interaction
The inhibition properties of ALS-2 to the swelling of bentonite were evaluated by linear expansion tests, etc

Summary

Introduction

The shale oil/gas exploration is developing rapidly in recent years. From the beginning, during the drilling, the stability of shale plays a very important role, and the stability control will affect the drilling costs greatly (Bol, 1986; Lal, 1999). Which are cheap, highly effective shale inhibitors for well-drilling timeframes, but they may lead to flocculation under high concentration, and the inhibition is not durable (Van Oort, 2003). Polyammonium has been developed as a kind of excellent clay expansion inhibitor, but these polymers adsorb on the surface of rock, block the formation, and reduce the permeability of reservoir. Some small molecular ammonium salts, as inhibitors for shale hydration, can avoid such defect above and exhibit ideal inhibitions without any poisonous or hazardous materials. The use of water-based drilling fluid can avoid the cost of oil contaminated drilled cuttings disposal (Wang et al, 2007; Zhang et al, 2015, 2007). The compatibility of the ammonium salt with traditional drilling fluid additives was evaluated.

Methods

Results

Conclusion