Novel Micro and Nano Particle-Based Drilling Fluids: Pioneering Approach to Overcome the Borehole Instability Problem in Shale Formations

Abstract

Oil-based mud (OBM) has strong inhibitive ability, which can prevent shale formations from hydration and swelling, and thus is often used in the development of shale gas reservoirs in China. Due to the low formation temperature (under 90 °C), high pressure (with pressure coefficient up to 2.2), long barefoot interval (up to 2138 m), borehole instability problem is easily encountered in dealing with the drilling of horizontal intervals of shale gas wells, which brings great challenges to drilling fluid technology. Maintaining wellbore stability is the most critical aspect of drilling operations of horizontal well intervals. However, most of OBM system can not prevent filtrate invasion into nano-sized pores and micro-fractures on shale surface, and subsequent cause borehole instability problems. The main reason is that conventional drilling fluid particles are too large to seal the nano-sized pore throats or micro-fractures in shales, and thus can not stop fluid invasion. A new type of composite particles is developed, and the mean particle diameter of composite particles is about 105.6 nm. These micro-nano particles (MNP) are added to OBM, and their influence on shale stability is evaluated. The core displacement experiment indicates that these micro-nano particles can reduce the shale permeability by a significant amount, and thus stop fluid invasion and inprove wellbore stability. The reason is that these particles are small enough to penetrate and seal the pore throats in shale, and built an effective internal mud cake possessing low permeability on shale surface, resulting in the reduction of filtrate penetration into the shale. The experimental results show that these particles can prevent pressure transmission and improve wellbore strength greatly. In addition, MNP have no effect on rheological properties of drilling fluids, and they are environmentally friendly, too. As a result, MNP can reduce fluid losses to the formation significantly, and consequently provide an excellent sealing effect, so MNP are an effective plugging agent for strengthening wellbore stability. Reduction of fluid losses and enhancement of wellbore strength can be achieved by addition of these micro-nano particles to oil-based drilling fluids. MNP-based drilling fluids have been successfully run for dozens of wells in Weiyuan-Changning and Shaotong shale block. The field application indicates that no borehole instability problems are encountered in the drilling process of horizontal well intervals. Using these MNP-based fluids containing micro-nano particles to seal the shale is a very powerful and economical approach to address borehole instability problem in troublesome shale formations. These MNP-based fluids are suitable for the drilling of long sections of horizontal laterals. In the future, the MNP-based drilling fluids might hold great promise to resolve shale instability problem.

Direct Pore-Level Visualization and Verification of In Situ Oil-in-Water Pickering Emulsification during Polymeric Nanogel Flooding for EOR in a Transparent Three-Dimensional Micromodel

“…Currently, nanoparticles (NPs) have been applied in many areas such as civil engineering, medical applications, − food science, and solar cells . It also appears to be an alternative for improving different engineering processes in the oil and gas industry, including reservoir characterization, reservoir management, drilling, , and completion process . Besides, the injection of NPs in the form of nanodispersions has also attracted the attention of being used as a potential EOR method due to its small size (1–100 nm) and many other promising interfacial properties. − Currently, it is widely accepted that the NPs could adsorb onto the interface of two immiscible fluids, − and this process helps recover more oil by reducing interfacial tension (IFT), ,,, altering wettability, − modifying disjoining pressure, , and stabilizing Pickering emulsions. − However, the mechanisms of NPs for extra oil recovery are still not well understood so that field applications are not widely applied and relevant research mostly is based on laboratory core flooding experiments. − …”

“…Currently, nanoparticles (NPs) have been applied in many areas such as civil engineering, 6 medical applications, 7−10 food science, 11 and solar cells. 12 It also appears to be an alternative for improving different engineering processes in the oil and gas industry, including reservoir characterization, 13 reservoir management, 14 drilling, 15,16 and completion proc-ess. 17 Besides, the injection of NPs in the form of nanodispersions has also attracted the attention of being used as a potential EOR method due to its small size (1−100 nm) and many other promising interfacial properties.…”

Study on the Mechanism of Ionic Stabilizers on Shale Gas Reservoir Mechanics in Northwestern Hunan

“…For example, some scholars used polymer to reduce water loss and inhibited its hydration expansion in shale drilling [11][12][13][14]. Some scholars use nano-compounds to maintain drilling stability to seal small holes in shale [15][16][17]. Other scholars utilized shale inhibitors such as surfactant, polyether and ammonium salt to improve the stability of the pore walls [18][19][20].…”

Application of Nano‐Polymer Emulsion for Inhibiting Shale Self‐Imbibition in Water‐Based Drilling Fluids

“…The need to find a feasible and effective method for inhibiting shale self‐imbibition has become an urgent task. Currently, with the fast development of nanotechnology, the application of various nanomaterials in the oil and gas industry is garnering considerable attention (Abdo & Haneef, ; Jain, Mahto, & Sharma, ; Vryzas & Kelessidis, ; Zhang et al, ). Compared with microemulsions, nano‐polymer emulsions (SDPE) have better high‐temperature stability and can be uniformly dispersed in drilling fluids (Liu, Qiu, & Huang, ).…”