Further tests of new method for zone isolation in horizontal wells

Abstract

This research is the continuation of Phase II of a joint industry project, whose main objective is to investigate the feasibility of sealing off water and gas producing zones in a horizontal well. During Phase I of the project laboratory experiments were conducted using PVC pipes up to 2-in. diameter and 3-ft. long in order to investigate the viability of using three commercial gels for use as wellborn plugs. The encouraging results from these earlier experiments led to testing the method in a full-scale 60-ft. long by 6-in. diameter wellborn model. The results obtained were again encouraging, but we needed to confirm them by repeating the experiment with some modifications. The two main objectives of this research are: (i) to investigate the effectiveness of K-MAX as a chemical wellborn plug and PERMSEAL as a formation gel in a horizontal well, and (ii) to measure the holding pressure of K-MAX. For the first research objective, the existing 60-ft. long apparatus was modified to include heater pipes inside the 12-in. PVC oboes to allow hot water circulation to achieve a temperature of about 120 F̊ during curing of PERMSEAL. The results showed that K-MAX performed satisfactorily as a chemical wellborn plug, being displaced with no slumping. The PERMSEAL was displaced radially around the wellborn, penetrating and consolidating the sand and making it apparently impermeable. The holding pressure apparatus consisted of two lengths of 5 []-in. casing (5-ft. long and 10-ft. long), open at one end and closed at the other. K-MAX gel was introduced into the pipe at the open end. Upon curing, the closed end was connected to a HPLC pump to inject water against the K-MAX plug. The holding pressures obtained were low (less than 1 psi). Somewhat higher holding pressures may be expected in the field because of the actual wellborn roughness; and with surface rams being closed during injection in the field, the formation would preferentially be injected into the problem zone. Given the encouraging results to date, it is recommended to field test the new zone isolation method.