Experimental Research Of The Damage Extent Of Rock Caused By Perforating

The unconventional oil and gas resources in our country have rich reserves and potential,while it has poor reservoir properties,low permeability of the matrix.Its distribution is dispersed.We can obtain the economic development of hydrocarbon accumulation only by using advanced technology,large-scale stimulation measures.The common stimulation means used are fracturing and horizontal well technology.Most of wells requiring hydraulic fracturing generally use perforated completion.Perforation is an important part of the oil and gas well completion.It also plays an important role on hydraulic fracturing and growth in production.In recent years,scholars found that pore structure and permeability of the rock surrounding the tunnel will change under the action of pressure and impact force of the explosion,in the study of perforating injury.The large pore is destructed while micro-cracks may be filled with particulate debris.Another scholars described the circumstances of injury from perforation relying on reducing the extent of rock intensity and permeability.But related research is not yet ripe.The unanimous conclusion about damage has not been obtained.The lack of research about perforation having influences on cracks form,number,width around the rocks.Understanding the relationship between the micro-cracks and crack propagation in hydraulic fracturing caused by perforation is still insufficient.In this paper,the main research is distribution of micro-cracks around perforation tunnels caused by perforation by means of laboratory experiment simulation method cement instead of natural rock in experiment.Experiment used logging HPHT perforating experiments on cement pressurization vessel perforation from Shengli Oilfield in order to simulate underground confining pressure,pore pressure and other parameters when perforating.In this paper,we use precast cross section method to observe radial cross-section of the perforation caused by circumferential distribution of crack,and analyzed mechanism of crack We observed cross section microscopic cracks of the sample by using portable digital microscope whose the highest magnification is 150 times.On the basis of perforating experiments,this paper analysed the effect of pore distribution around the crack of crack propagation initiation pressure and impact as well as micro-cracks slit width of openings around the permeability and fracture initiation pressure,estimated the rock permeability around tunnel according to the seam width and the crack density,analysed the distribution law of the crack position and the effect of fracturing operation pressure.