Correlations To Predict Frictional Pressure of Hydraulic Fracturing Slurry in Coiled Tubing

摘要

Compared with conventional tubing fracturing, coiled tubingrn(CT) fracturing has several advantages. CT fracturing hasrnbecome an effective stimulation technique for multi-zone oilrnand gas wells. CT fracturing is also attractive productionrnenhancement method for multi-seam coalbed methane wells asrnwell as wells with bypassed zones. The excessive frictionalrnpressure loss through CT has been a concern for CTrnfracturing. CT strings have small diameter and this limits therncross-sectional area open to flow. Furthermore, the tubingrncurvature causes secondary flow and hence results in extrarnflow resistance. This increased friction pressure results in highrnsurface pumping pressure. The maximum possible pump raternand sand concentration, therefore, have to be reduced. Tornproperly design a CT fracturing job, it is, therefore, essentialrnto be able to predict the frictional pressure loss through CTrnaccurately.rnThis paper presents two correlations for the prediction ofrnfrictional pressure of fracturing slurries in coiled tubing. Onernis developed based on full-scale slurry flow tests with 1-1/2-rnin. coiled tubing and slurries prepared with 35 lb/Mgal guarrngel. The extensive experiments were conducted at the fullscalerncoiled tubing flow test facility. The other correlation isrnderived from the Srinivasan's friction factor correlation ofrnNewtonian fluid in coiled pipes. The Srinivasan correlation isrnmodified for the non-Newtonian fluids and it further requiresrnan inclusion of the relative slurry viscosities which have beenrnthoroughly evaluated in this study. The proposed correlationsrnhave been verified with the experimental data and actual fieldrnCT fracturing data. Case studies of wells recently fracturedrnusing CT are provided to demonstrate the application of therncorrelations. The correlations will be useful to the CTrnengineers in their hydraulics design calculations.