Enhancing Gas Production in Coal Bed Methane Formations With Zeta Potential Altering System

Abstract

This paper describes lab studies and field results on how a new Zeta Potential Altering System (ZPAS), utilized in fracturing treating fluids, improves gas rate production. Lab and field results show ZPAS minimizes proppant flow back and coal fines migration, enhances fluid load recovery, and inhibits calcium carbonate scale formation. The mechanism of this system based on an inner salt that modifies the Zeta Potential on particles such as frac sand and formation substrate, changing the charge towards neutral values and therefore enhancing particles agglomeration. This paper also shows how the Zeta Potential Altering System has been applied in numerous coalbed methane wells which were treated by refracturing. The ZPAS has been run in borate cross-linked fluids and linear gel systems. Field results have been positive on wells treated, with less time to clean out frac sand, less flow back sand and coal fines, higher conductivity after load fluid recovery, and higher gas productivity after load fluid recovery and de-watering of CBM Zones. Production has increased up to 15 fold on individual wells with 3 to 20 months production history. IntroductionSeveral factors may affect the productivity of a fractured well. 1-7 Invasion of fines into proppant pack affects the permeability, resulting in early decline in well productivity. Besides this, conductivity of fractured wells with 16/30-mesh standard sand could be significantly decreased when crushed at closure pressures. Invasion of coal fines and proppant may result in early downhole mechanical pump failures. Current approaches to the problem of coal fines and proppant flow back have been flowback preventative additives such as; fibers, resin consolidation systems, ceramic proppants, and resin-coated proppants. Different proppant coating systems have been designed to control the movement of fines generated from crushed proppant: polymer based tacking agents, phenolic resins, furan resins, epoxy resins, and urea-formaldehyde resin among others. These systems also prevent proppant flowback. 8

Critical Conditions for Massive Fines Detachment Induced by Single-Phase Flow in Coalbed Methane Reservoirs: Modeling and Experiments

“…Due to hydrophobe interactions through VDW bonds, a strong molecular hook-and-latch system is formed between fines and the fracture surface, thus providing an increased adhesive force . Several experimental and field studies have demonstrated that chemical methods successfully prevent fines migration, even under high flow rates and flow interruptions, with no observed reduction in permeability. − …”