Nano-Film-Forming Plugging Drilling Fluid and Bridging Cross-Linking Plugging Agent Are Used to Strengthen Wellbores in Complex Formations

Abstract

Lost circulation is one of the great challenges during the drilling process as it can not only increase the risk of drilling operations but also cause an increase in drilling costs, thus greatly affecting the drilling efficiency. Wellbore strengthening has been widely used to prevent lost circulation, which ultimately expands the mud density window by increasing the formation fracture pressure. This paper proposes a combination of “preventive” wellbore strengthening and “remedial” wellbore strengthening to prevent leakage and plug and stabilize wellbores by means of summarizing the characteristics of lost circulation and wellbore instability in the Hasan area. The formula of the bridging cross-linking plugging agent is determined by experiments as well slurry + 8–10% granular material + 3–5% fiber material + 2–4% elastic material + 0.5–1% cementing material. The formula of the nano-film-forming plugging drilling fluid is determined to be 3% bentonite + 0.2NaOH + 0.2% KPAM + 3% SMP + 1% PB-1 + 2% SMNA-1 + 2% lubricant SMLUB-1 + 1% modified nano-SiO 2 particles. Then, the performance evaluation of the composite system is carried out by the high-temperature and high-pressure plugging simulation evaluation device. The results show that the bridging and cross-linking plugging agent can effectively block the 1–3 mm crack, the pressure-bearing capacity is greater than 10 MPa, and the anti-liquid return capacity is greater than 4 MPa. The nano-film-forming plugging drilling fluid has lower fluid loss and better rheological properties.

Synthesis and Plugging Performance of Nano-Micron Polymeric Gel Microsphere Plugging Agents for Oil-Based Drilling Fluids

“…Conventional plugging materials, such as silica [ 15 ], ultrafine calcium carbonate [ 16 ], oxidized asphalt [ 17 ] and modified graphene [ 18 ], failed to deliver desirable plugging performance due to relatively uniform (narrow) particle size distribution, low deformability and inferior dispersion capacity. Nonetheless, the research and application of nano-organic plugging agents for OBFs had delivered some promising results.…”

Research and Application of Fast Plugging Method for Fault Zone Formation in Tarim Basin, China

“…5 fault zone, the existing leakage-plugging technology mainly includes bridge plugging, cement slurry, chemical consolidation, high filtration, gel and other systems, and there are problems such as inconsistent effects, instability and leakage recovery in the application process of the systems [20,21]. Based on an analysis of plugging effects, these five types of plugging systems have their own advantages, but they all have defects, mainly including the following problems: (1) bridging plugging: using drilling fluid to prepare the plugging slurry, the requirements of water loss and wall building of the drilling fluid and the rapid accumulation of plugging particles to form a plugging barrier contradict each other, resulting in elongation and low strength of the plugging belt and easy occurrence of backflow [22,23]; (2) cement slurry plugging: cement slurry is an important method to solve malignant leakage, but on the premise of ensuring wellbore safety, cement slurry needs to ensure a certain waiting time, and it is easy to spit back and transmit wellbore pressure to connect fractures when cement slurry is not cemented [24]; (3) high-filtration plugging and chemical consolidation: under many conditions, these two kinds of plugging are used in combination, but porous or fibrous materials with high filtration make it easy to seal the door at the joint, resulting in false plugging [25,26]; and (4) gel plugging: gel plugging has solved many malignant leakage problems on sites, but its own strength has certain defects, which mean it cannot be used alone to solve the plugging problem [27,28].…”

Hydrodynamic Analysis and Cake Erosion Properties of a Modified Water-Based Drilling Fluid by a Polyacrylamide/Silica Nanocomposite during Rotating-Disk Dynamic Filtration

“…During filtration, solid particles in the drilling mud settle on the borehole wall and form a thin mud cake. The mud cake is the first barrier to prevent the increase of drilling mud filtration due to its low permeability. − Increasing drilling mud filtrates generally causes various problems such as damage to the oil production zones, fluid invasion into water-sensitive layers such as shales, and causing the drill string to be stuck due to thick mud cake formation. , Due to the importance of the topic, researchers have concentrated on nanoparticles (NPs) as a new additive to reduce fluid loss. − …”