Abstract
The major low molecular inhibitors showed inhibition in the hydration of clay in the laboratory for water-based drilling fluids, according to the principle of intercalation adsorption. However, inhibitors have failed and caused serious engineering accidents in drilling oil and natural gas. This paper investigated the transmission of several of drilling fluids to indicate whether low molecular inhibitor for drilling can effectively inhibit the wellbore hydration. The inhibition of drilling fluid with the plugging of mud cakes, was significantly weakened based on the hydration expansion of cores and cutting recoveries. The residual contents of inhibitors were determined with the precolumn derivation of high-performance liquid chromatography (HPLC) analysis and were chartered with Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) analysis in the structure of the derivative. The clogging behavior of the mud cake was described by environmental scanning electron microscopy (ESEM). Experiments show that 40 wt% to 90 wt% by weight of the corrosion inhibitor cannot pass through the mud cake in the dynamic filtration of the drilling fluid. The mud cake can be further divided into a nanostructure layer, a homogeneous layer and an anisotropic layer with different permeability. Most inhibitors should be limited to the nanostructure layer and the homogeneous layer.
Highlights
IntroductionSometimes called the blood of drilling, acts to carry cuttings, lubricate, and balance pressure
Drilling fluid, sometimes called the blood of drilling, acts to carry cuttings, lubricate, and balance pressure
With the low efficiency of inhibitors on the collapsing of wellbores, this paper investigated whether low molecular for drilling fluid could effectively interact with wellbores
Summary
Sometimes called the blood of drilling, acts to carry cuttings, lubricate, and balance pressure. During drilling with water-based drilling fluid, wellbore instability is a serious problem in drilling shale oil or gas, and can lead to a series of problems such as breakage, fracture development, water-sensitivity, and leakage problems [1,2,3]. Shale is rich in hydrophilic clay minerals (illite, montmorillonite), excellent nanopores, and has a large specific surface area [4]. Shale is hydrated, which results in the expansion and dispersion of clay minerals and eventually leads to the collapsing of the shale [5,6]. Based on the adsorption mechanism of hydration intercalation of clay lattice, various types of small molecular surface hydration inhibitors have been developed for water-based drilling fluid [7,8,9,10].
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