Experimental Simulation Of Plugging Reservoir Leakage And Optimization Of Plugging Slurry

Fractured reservoirs have widely distribution and abundant hydrocarbon resources. When faced with fractured reservoir during drilling, often associated with the occurrence of leakage, cause serious damage to reservoir and put off reservoirs discovered in time, accurate evaluation and highly efficient development. How to effectively block reservoir fracture, reduce the damage to reservoir from drilling and completion fluid, is urgently needs to be solve. Under the different pressure between wellbore and reservoir, dynamic crack width can be extended from the micron level to millimeter level, led to plugging material is difficult to stranded in the fracture, Reduce the blocking layer stability. It is important to choose plugging material with the dynamic crack width extended from micron level to millimeter level reasonable. Therefore, simulations of plugging experiment were conducted, optimization plugging slurry formulation, has important practical significance for safety drilling and reservoir protection.The object of this thesis is the Jiulong mountain structure of pearl group compact conglomerate gas reservoir, has been clear about the dynamic width range of fracture in fractured reservoir through stress sensitive experiment and finite element simulation. Conducted the crack sealing experiment from micron level to millimeter level width, and plugging material combination synergy mechanism were analyzed. Puts forward a new fracture plugging idea about add support particles in advance. Summarize and put forward optimization index for plugging slurry according to two level of fracture width. Outline the roadmap of plugging material optimization method, formed the plugging slurry formulation optimization strategy according to fractured reservoir.We define the dynamic variation range of the reservoir fractures width. To determine the crack width under the in situ condition of effective stress is2.70-15.91μm through stress sensitivity experiment with small core column and full diameter core. Considering the dissolution, the crack width increase120-300μm. The finite element simulation analysis show that Reservoir dynamic crack width from several hundred microns to millimeter level under the different pressure between wellbore and reservoir.We develop a full diameter core plugging instrument which can model the fracture plugging process under high temperature and high pressure. Design the plugging experiments for fracture width from micron level to millimeter level. For micron level of cracks width, it can be satisfied with plugging requirement through add temporary plugging material which is match the seam width to the original drilling and completion fluid, pressure-bearing capacity15MPa. After the acid dissolved plugging, permeability recovery reach80%. For millimeter level of cracks width, it can be satisfied with plugging requirement through synergy between rigid particles, fibers and elastic particles. In the2mm wide sealing experiments, the pressure-bearing capacity arrive13MPa, the cumulative loss only30mL by the composition with original drilling and completion fluid+5%rigid particles+4%soft fibers+0.5%hard fibers+3.5%elastic particles. We put forward and verify a new fracture plugging idea that adding supporting lost circulation material in advance to bridge the fracture open. Add high strength and inertia bridging particles in drilling and completion fluid, it can remain after acid defuse plugging layer in cracks and supporting the cracks, reducing the negative impact of reservoir stress sensitivity after the flow back and keep the flow conductivity of fracture. Using high temperature and high pressure full diameter core fracture plugging instrument for experimental verification, the result show that crack width does not change during flow back process.We outline a roadmap for plugging material optimization. According to the result of plugging experiments, analyzes the rigid particles, fibers and elastic particles impact on the stability of the blocking layer, and expounds the synergy mechanism of different plugging materials. Further from the plugging material geometry, mechanical properties and chemical properties, puts forward the optimizing method of plugging material in plugging slurry. Summarize and put forward optimization index for plugging slurry according to two level of fracture width, formed the plugging slurry formulation optimization strategy according to fractured reservoir.