Evaluation of Preflushes for Sand Consolidation Plastics

Abstract

In a laboratory study of various organic compounds to be used as a plastic preflush, ethylene glycol monobutyl ether-EGMBE-was found best suited for preflush, ethylene glycol monobutyl ether-EGMBE-was found best suited for the purpose. Because it is a mutual solvent, it cleans the sand and makes the mineral surfaces more accessible to the consolidating plastic. It is convenient, versatile, and effective. Summary and Conclusions A laboratory study of the effectiveness of commercially available plastics in achieving consolidation of formation material has shown that more effective preflushing of the unconsolidated matrix can enhance preflushing of the unconsolidated matrix can enhance plastic performance. Several different organic plastic performance. Several different organic compounds were considered as candidates for use as a plastic preflush; ethylene glycol monobutyl ether plastic preflush; ethylene glycol monobutyl ether (EGMBE) was found to be best suited for the intended purpose, being convenient to use, versatile, and purpose, being convenient to use, versatile, and effective EGMBE is a mutual solvent; that is, it has solvency for both aqueous and nonaqueous materials. Because of this property, EGMBE cleans the sand and miscibly displaces residual water, resulting in enhanced accessibility of the mineral surfaces to the sand consolidation plastic. EGMBE also increases the permeability of formation material; this effect is most permeability of formation material; this effect is most pronounced in samples that contain an appreciable pronounced in samples that contain an appreciable concentration of nonquartz components (clays, feldspars, or carbonates).EGMBE has been used successfully in the laboratory and field as preflush for both 35 percent p-f and 55 percent p-f plastics (premixed phenol-formaldehyde-plastics). percent p-f plastics (premixed phenol-formaldehyde-plastics). It is the only preflush that has been used in conjunction with the EPR Epoxy sand consolidation process. It was also found that EGMBE improved laboratory consolidations performed with another commercially available system performed with another commercially available system (an externally catalyzed phenol-formaldehyde plastic). This preflush is especially beneficial in a well that requires acidizing before plastic consolidation. Preflush Evaluation Preflush Evaluation Laboratory Test Procedure To make the results of this study as applicable to field operations as possible, rubber-sleeve core barrel formation samples, instead of synthetic blends, were extensively used. For comparison, a few experiments were conducted with a clean, high-silica sand. Also, a few produced sand samples were used instead of rubber-sleeve core barrel samples. The formation samples were cleaned slightly before use. Cleaning consisted of removing obviously extraneous material and air drying in an oven. Some of the sample characteristics, including clay mineral content determined by X-ray diffraction, are shown in Fig. 1.The experimental equipment used in this investigation permittedmeasurement of initial permeability,plasticizing, andmeasurement of permeability,plasticizing, andmeasurement of consolidated sample permeability - all in sequence without disturbing the sample. As a final step, each consolidated sample was removed from the holder and its compressive strength measured. (The details of this laboratory procedure are given in Appendix A.) Each holder accommodated a 1-in.-diameter X 3 5/8 in-long sample of unconsolidated sand. The flow system was deigned for one to eight sample holders which were connected in parallel and manifolded so as to permit selective flow of fluids in either direction (corresponding to production or injection). P. 1095