Experimental Study Of Conductivity Of Temporary Blocking Support Fractures And Its Influencing Factors

In order to fullly use the production potential of old oil fields that have already been at the high water-cut stage.It is necessary to control the water content and develop the oil production which is re-fracturing technology.The temporary plugging agent is to plug the original fractures,create new fractures or change the direction of fractures,it can meet the requirement of re-fracturing what is to control the water content and develop the oil production.In this paper,the evaluation of experiment of proppant conductivity with the API diversion chamber and the fracturing core are conducted firstly.Then temporary plugging agent was placed in the diversion chamber,the surface of the core fractures,and the surface of the supporting fracture to implement experiment to gain the mechanism and performance of temporary plugging agent.Finally further evaluate the influence factors of the temporary plugging agent by using the fractal dimension,we can get the following understandings and results:(1)There is a great influence on conductivity with fluid properties which is obviously related to the viscosity and density.The greater of viscosity,the less of conductivity,and the broken rate is more when the fluid is wet;Different proppants filled in one fracture,the decrease of conductivity is more when fluid is wet.(2)In this paper,the starting pressure gradients of oil permeable-water repellent proppant which is in the range of 1.69~18.28*10~-44 MPa/m,and it can certainly resist water.The greater closing pressure and the greater starting pressure,it shows better power function relationship between the two.(3)The decrease range of the conductivity of the pure fracture is 98%to 99%,and the filled proppant fracture is between 30%and 35%,the fracture conductivity increased by 2-5order of magnitude.The more of closure pressure,the bigger of increase,it means proppants have decisive influence on conductivity.(4)The gel particles completely expanded in the formation water with 24 hours,then placed it in kerosene the expansion ratio of gel powder dropped rapidly,quality of gel particles for expansion of only 78%.The blocking ratio of powder to fractures is in a range of95%~100%,and the unblocking ratio is high which means the gel powder can be used as a temporary plugging agent in re-fracturing.(5)The gel has great influence in temporary plugging,when filled proppant is cerasite the blocking ratio of gel powder to fracture is 85%and the unblocking ratio is 96.7%;when filled proppant is quartz sand the blocking ratio of gel powder to fracture is 76%and the unblocking ratio is 74.2%,when filled proppant is oil permeable-water repellent proppant the blocking ratio of gel powder to fracture is 38%and the unblocking ratio is 45%,when filled proppant is coated quartz sand the blocking ratio of gel powder to fracture is 45%and the unblocking ratio is 22%.When the wetness of proppant is same as gel the blocking rate and recovery rate is more,and the properties of temporary plugging is the best when filled ceramsite.(6)The temporary plugging of gel for fracture filled different proppant has a lot to the porous structure and surface properties of proppant,The porous occupied structure formed with quartz sand?ceramsite and gel powder,the powder revolved structure formed with oil permeable-water repellent proppant and coated quartz sand with gel particles.And the porous structureis better.(7)There is the most suitable concentration of temporary plugging agent which can make the best plugging effect and no damage to information.In this paper the most suitable concentration of temporary plugging agent is 0.75 kg/m~2.(8)The blocking rate of gel for fracture is rising gradually with the rising confining pressure.When the proppant is oil-wet,the increase of plugging rate ring pressure increases exponentially;When the proppant is water-wet,the increase of plugging rate ring pressure increases logarithmically.(9)The larger fractal dimension of fractures,the more decrease in fracture conductivity and the effective fracture width when filled with gel particles;The smaller fractal dimension of fractures,the bigger fractal dimension of new surface after filled the same proppant and gel powder,it shows the more fractal dimension,the more decrease range of conductivity.