Frac-pack Sand Control And Stimulation Techniques

Sand production during the exploitation of oil and gas fields is detrimental to productivity index of well. In order to avoid negative effects of sand production on production sand control completion must be introduced. Among the sand control methods cased hole gravel packing is a common one. Although it has many advantages such as its effectiveness of sand control and very long duration of sand control, CHGP leads to a well productivity index decrease. Therefore, a new sand control completion was presented. The new method combines hydraulic fracture with cased hole gravel packing.This dissertation discussed the feasibility of sand control with frac and pack. Main work included mechanism study of sand control and stimulation of frac & pack, selection of material, tip screen-out fracture design and economic evaluation.In comparison to gravel pack, frac & pack communicates well bore with pay formation by a high conductivity fracture packed with gravel. It bypasses near-well damage, and decreases the resistance when reservoir fluid flows through porous medium and thus increases well productivity.Except that the usual function of preventing formation sand from entering production string, frac &pack can also prevents formation from sand production by altering flow pattern, decreasing drag force exerted on rock matrix and decreasing sand -carrying capacity of reservoir fluid.Based on skin analysis of grave pack completion, a productivity prediction model was presented to analyze skin effect on well productivity. The results imply that the bulk completion skin in low-permeability formation primarily consists of drilling damage. While, the bulk skin in high-permeability formation consists of drilling damage, perforation and gravel pack damage.A model was formulated which could be used to predict whether the interest formation produced sand. In-situ stress, liquid pressure in borehole and pore pressure near well-bore were taken into account in the model. Drucker-Prager strength criterion was used to judge the critical state of near-well rock. Sensitivity analysis imply that fracture length is in proportional to sand production critical rate . decrease in the formation strength will result in a steep decline of critical rate.According to fluid type and formation permeability different model was adopted to depict fracture fluid leakoff into formation. Pressure independent fluid leakoff model was introduced to depict linear fracture fluid leakoff into high-permeability formation. The others were depicted by carter fluid leakoff model.Heat transfer in vertical direction was incorporated while establishing the wellbore temperature field model. After dicretization of the mathematical model differential equation could be solved by strongly implicit procedure technique. At the same time,K-D-R temperature profile model in fracture was improved in order to facilitate computation procedure.Constitution of fracture damage is comprehensively analyzed and was incorporated in productivity prediction model. Results indicate chocked fracture is severely detrimental to fractured well productivity while fluid leak-off damage has less side effect on well productivity.During fracture inflation and pack stage, fracture geometry could be simulated base on matter balance law.An economic evaluation model was formulated and economic benefit of frac & pack was analyzed by the model. Although costs of frac and pack are bigger than that of gravel pack, this additional expenditure is justified.A field case was presented to validate theory and arithmetic presented in this dissertation. The results imply that critical rate of frac and pack completion is the double of that of conventional gravel pack. Productivity index of frac &pack well is as high as that of openhole completion, hi a word, frac & pack provides a preferable sand control mechanism to conventional cased hole gravel pack.