Experimental study on an oil‐based polymer gel for lost circulation control in high‐temperature fractured formation

Abstract

Aiming at the lack of plugging agent for oil‐based drilling fluid leakage in fractured formation, an oil‐based gel‐plugging agent with high structural strength and strong thermal stability was synthesized based on monomer polymerization and crosslinking. According to the preparation experiment, when the total concentration of methyl methacrylate (MMA) and butyl acrylate (BA) is 30% and the ratio is 6:4, the oil‐based gel solution can be completely gelatinized from 80 to 200°C, which has high gel strength and controllable gelation time. The effects of total concentration of BA and MMA, the ratio of BA and MMA, synthesis temperature, oil‐based drilling fluid invasion, shear effect, and fiber concentration on gelling performance were systematically studied. Fourier transform infrared molecular structure analysis showed that the oil‐based gel contained benzene ring group and ester characteristic group. From the rheological properties of oil‐based gel with 30% gelling agent at 160°C, it could be seen that the elastic modulus G′ of 10 Hz is 232 kPa, which is much larger than the storage modulus G″ is 99 kPa, which reflects the solid properties and has good elasticity and high strength. The displacement experiment of sand filling pipe and dynamic and static plugging experiment of high temperature and high pressure shows that the oil‐based gel has high bearing capacity in fractures and sand filling pipe. The bearing pressure is 3.01 MPa in 6 mm fractures, and the bearing pressure gradient is 0.602 MPa/cm.

Temperature-Responsive Nano-SiO2 Composite for Improving Shale Stability in Oil-Based Drilling Fluids

“…In recent years, the exploitation of unconventional low-permeability oil and gas resources (such as shale gas) has received specific attention. , Compared with water-based drilling fluids (WBDFs), oil-based drilling fluids (OBDFs) have significant advantages in stabilizing wellbore, preventing sticking and inhibiting shale hydration expansion. − However, due to shale instability and widespread development of microfractures in formations, fractures are easily induced during drilling process, resulting in the loss of drilling fluids. The petrological properties of shale caused by the lack of drilling fluids would further increase the leakage, leading to huge economic issues, delaying the drilling cycle, and sometimes even affecting reservoir production. − …”

Synthesis and performance evaluation of water‐absorbing resin coated with polymethyl methacrylate as a lost circulation material

“…After the volume expansion, the material is squeezed into the formation fracture and further expanded, which plays a role of plugging and bracing. This feature makes it adaptive to the size of lost circulation channel and is applicable to porous and fractured formations 14–18 . The most common liquid‐absorbing material is water‐absorbing/oil‐absorbing resin.…”

“…This feature makes it adaptive to the size of lost circulation channel and is applicable to porous and fractured formations. [14][15][16][17][18] The most common liquid-absorbing material is water-absorbing/ oil-absorbing resin. Lai et al developed a dual-network water-absorbing resin (DNWR), which is composed of two independent cross-linked networks and has good mechanical properties and temperature resistance.…”

Sodium alginate as an eco-friendly rheology modifier and salt-tolerant fluid loss additive in water-based drilling fluids

“…3,4 Among these drilling uids, WBDFs are considered to be the most widely recommended owing to their desirable properties such as lower cost, ease of preparation, variable rheology, and eco-friendly nature. [5][6][7][8] To minimize formation damage and stabilize the borehole, satisfactory rheological and ltration performance in WBDFs should be given priority during circulation.…”