Abstract
In order to mitigate the loss circulation of oil-based drilling fluids (OBDFs), an oil-absorbent polymer (OAP) composed by methylmethacrylate (MMA), butyl acrylate (BA), and hexadecyl methacrylate (HMA) was synthesized by suspension polymerization and characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and scanning electronic microscopy (SEM). The oil-absorptive capacity of OAP under different solvents was measured as the function of temperature and time. The effect of the OAP on the rheological and filtration properties of OBDFs was initially evaluated, and then the sealing property of OAP particles as lost circulation materials (LCMs) was examined by a high-temperature and high-pressure (HTHP) filtration test, a sand bed filtration test, a permeable plugging test, and a fracture sealing testing. The test results indicated that the addition of OAP had relatively little influence on the rheological properties of OBDF at content lower than 1.5 w/v % but increased the fluid viscosity remarkably at content higher than 3 w/v %. It could reduce the HTHP filtration and improve the sealing capacity of OBDF significantly. In the sealing treatment, after addition into the OBDF, the OAP particles could absorb oil accompanied with volume enlargement, which led to the increase of the fluid viscosity and slowing down of the fluid loss speed. The swelled and deformable OAP particles could be squeezed into the micro-fractures with self-adoption and seal the loss channel. More important, fluid loss was dramatically reduced when OAP particles were combined with other conventional LCMs by a synergistic effect.
Highlights
In oil and gas drilling engineering, one of the frequently encountered problems is lost circulation, which is defined as the undesirable partial or complete loss of drilling fluid into formation voids during drilling, circulation, running casing, or cementing operations [1,2]
The results indicated that oil-absorbent polymer (OAP) had a good thermal stability and could be used in
The difference of filtrate rate between static and dynamic filtration was not clear, whereas, it was obvious that OAP was capable of reducing high-temperature and high-pressure (HTHP) fluid loss more effectively than modified lignite and asphaltic additive under both static and dynamic conditions
Summary
In oil and gas drilling engineering, one of the frequently encountered problems is lost circulation, which is defined as the undesirable partial or complete loss of drilling fluid into formation voids during drilling, circulation, running casing, or cementing operations [1,2]. Other types of materials including cement, chemically activated cross-linked pilles, cross-linked cement, deformable-viscous-cohesive systems, nano-composite gel, gunk squeezes [17], polyurethane grouting, crosslinked gel, viscoelastic surfactant, nano-particles [18], reticulated foam [19], and shape memory polymers [20] have attracted attention These materials are generally added either to the drilling fluid or separately in the form of a sweep or a treating pill [21]. A variety of materials have been used as LCMs, materials specially designed to combat lost circulation in invert-emulsion drilling fluids are relatively fewer than that for water-based drilling fluids [25]. Considering the similar properties between oil-absorbent resin and water-absorbent resin, the object of the current study is to probe the feasibility of oil absorbent resin in mitigating the loss of OBDFs
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