Abstract
In this paper, a liquid-solid phase-change autogenous proppant fracturing fluid system (LSPCAP) was proposed to solve the problems that was caused by "sand-carrying" in conventional fracturing technology in oil and gas fields. The characteristic of the new fluid system is that no solid particles will be injected in the whole process of fracturing construction except liquids. The fluid itself will transform into solid particles under the formation temperature to resist the closure stress in the fractures. There are two kinds of liquids that make up the new fracturing fluid system. One of the liquids is called phase-change liquid (PCL) which occurs in the liquid-solid phase change under the formation temperature to form solid particles. Another is called nonphase-change liquid (NPCL) which controls the dispersity and size of PCL in the two-phase fluid system. Based on the molecular interaction theory and organic chemistry, bisphenol-A epoxy resin was selected as the building unit of the PCL, and the NPCL consisted of deionized water + nonionic surfactant. The test results indicated that the new fracturing fluid shows the properties of non-Newtonian fluid and has no wall-building property. The new fluid system has good compatibility with the formation fluid, conventional fracturing fluid, and hydrochloric acid. Through the filtration test, the filtration coefficients of PCL, NPCL, and mixture are found to be 1.56 × 10(-4) m/s(1/2), 2.66 × 10(-4) m/s(1/2), and 1.7 × 10(-4) m/s(1/2), respectively, and the damage rate of mixture and NPCL is 18 and 17.7%. The friction test results show that the resistance reduction rate reaches 69% when the volume ratio of PCL and NPCL is 1:10. The shear rate and time only affect the size of the autogenous solid particles, and the sorting coefficient (S) of the particles is 1.04-1.73, indicating good sorting. Crushing resistance and conductivity test results show that the crush rate of autogenous solid particles is 3.56-8.42%. The conductivity of the autogenous solid particles is better than those of quartz sand and ceramsite under a pressure of 10-30 MPa.