Method for hydraulic fracturing and mitigating proppant flowback
Design method for hydraulic fracturing of a reservoir is presented that maximize well production rates and minimize proppant flowback. The method comprises employing computer simulators that analyze a fracturing treatment design in the context of well properties, reservoir properties, fluids and proppants, and calculates a critical filtration velocity for a proppant pack. If the fluid flow velocity in the fracture exceeds the critical filtration velocity, there is a risk for proppant flowback. The method is applicable to wells that have not yet been fractured, as well as those that have previously undergone a fracturing treatment.
1 . A method for fracturing a subterranean well, the method comprising:
(i) designing a fracturing treatment for stimulating a reservoir, the fracturing treatment comprising creating a fracture, design parameters for the fracturing treatment comprising at least one of: proppant concentration, fluid viscosity, flow rate, job stages, final fracture geometry, or one or more combinations thereof;
(ii) performing a computer simulation of the fracturing treatment, wherein the performing comprises generating a prediction of at least one of: fracture propagation, proppant distribution, fluid distribution, or fracture conductivity distribution;
(iii) setting flowback design parameters comprising bottomhole or wellhead pressure, flowback time, and flowback duration;
(iv) determining a critical filtration velocity u c for each computation cell for a final fracture geometry;
(v) determining a fluid production flow rate and a proppant flowback volume for specified flowback conditions; and
(vi) computing a recovered proppant volume V s and fluid production Q f at a near-wellbore boundary by repeating stages (iv) and (v) for consecutive intervals of flowback duration; and one of:
(vii) responsive to V s <V c and Q f >Q min , performing the designed fracturing treatment, where Q min is a minimum acceptable fluid production rate and V c is a maximum acceptable proppant flowback volume; or
(viii) responsive to V s or Q f not satisfying conditions stated in stage (vii), repeating stages (i)-(vi) with adjusted fracturing design parameters.
2 . The method of claim 1 , wherein the critical filtration velocity u c depends on parameters comprising at least one of: wall stress, effective proppant diameter, fracture width, fluid viscosity, proppant embedment, or one or more combinations thereof.
3 . The method of claim 1 , wherein, during computer simulations, predicted proppant flow velocities slower than the critical filtration velocity u c indicate zero proppant mobility in the fracture.
4 . The method of claim 1 , wherein the computing the recovered proppant volume V s is performed using parameters comprising at least one of: fracture surface area, fracture width, proppant pack permeability, fluid viscosity, reservoir compressibility, reservoir porosity, reservoir pressure, effective proppant size, or one or more combinations thereof.
5 . The method of claim 1 , wherein stage (i) further comprises obtaining mechanical and conductive properties of the reservoir, well trajectory, and placement of casing perforations.
6 . The method of claim 1 , wherein stage (i) further comprises collecting laboratory data corresponding to fluid properties and proppant properties.
7 . The method of claim 1 , wherein stage (i) further comprises selecting a hydraulic fracturing schedule.
8 . A method for fracturing a subterranean well, the method comprising:
(i) obtaining a design for a previously-performed fracturing treatment for stimulating a reservoir;
(ii) performing a computer simulation of the fracturing treatment, the performing comprising generating a prediction of at least one of: fracture propagation, proppant distribution, fluid distribution, and fracture conductivity distribution;
(iii) setting flowback job design parameters comprising bottomhole or wellhead pressure, flowback time, and flowback duration;
(iv) determining a critical filtration velocity u c for each computation cell for a final fracture geometry;
(v) determining a fluid production flow rate and a proppant flowback volume; and
(vi) computing a recovered proppant volume V s and fluid production Q f at a near-wellbore boundary by repeating stages (iv) and (v) for consecutive intervals of flowback duration; and one of:
(vii) responsive to V s <V c and Q f >Q min , performing the flowback job as designed, where Q min is a minimum acceptable fluid production rate and V c is a maximum acceptable proppant flowback volume; or
(viii) responsive to V s or Q f not satisfying conditions stated in stage (vii), repeating stages (iii)-(vi) with adjusted flowback job design parameters.
9 . The method of claim 8 , wherein the design parameters from the previously-performed fracturing treatment comprise at least one of: proppant concentration, fluid viscosity, flow rate, job stages, fracture geometry, or one or more combinations thereof.
10 . The method of claim 8 , wherein the critical filtration velocity u c depends on parameters comprising at least one of: wall stress, effective proppant diameter, fracture width, fluid viscosity and proppant embedment, or one or more combinations thereof.
11 . The method of claim 8 , wherein, during computer simulations, predicted proppant flow velocities slower than the critical filtration velocity u c indicate zero proppant mobility in a fracture.
12 . The method of claim 8 , wherein the computing the recovered proppant volume V s is performed using parameters comprising at least one of: fracture surface area, fracture width, proppant pack permeability, fluid viscosity, reservoir compressibility, reservoir porosity, reservoir pressure, mean proppant size, or one or more combinations thereof.