Research On Fluid Damage Mechanism In Shale Reservoir Fracture

Shale reservoir is generally need to undertake large-scale hydraulic fracturing to get complex fracture network system,in this way it can achieve a higher capacity.There are a large number of narrow fractures which connect the rock matrix and high wide fractures cannot be effectively supported even with small particle size of proppant,But those narrow fractures are of great significance to ensure effective reservoir volume and production stability.Therefore,the influence of fracturing fluid to low concentration proppant fractures will be the key research content in this paper.The shale samples were selected from the outcrop of chongqing northeast.They were the Longmaxi shale,the Lujiaping shale and Xujiahe shale.The shale mineral composition was analysised by X-ray diffraction.CEC test and CST test were conducted to analysis shale hydration characteristics of clay minerals and cation exchange properties.On the basis of understanding the shale mineral properties,spontaneous imbibition,hardness test and triaxial stress test were conducted to analysis the influence of fluid on the mechanical properties of shale.The proppant embedment experiment was conducted under different conditions,such as shale type,testing liquids and soaking time.The roughness of fracture surface were scanned with Laser scanner.Nitrogen was used to measure the undamaged fracture conductivity.Fluid was injected into the fracture after nitrogen to simulate the damage process.Mathematical models for calculating the proppant embedment and fracture conductivity were established and campared with the experimental results to verify the reliability of the mathematical models.