New Matrix Sealing Materials Applicable To Both Injection And Producing Wells
Authors: Stewart J.D. , Eilers L.H. 
Published: December 2007

American Institute of Mining, Metallurgical and Petroleum Engineers, Inc.
Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines.

Abstract
New, low-cost, easily-applied matrix sealing materials have proved highly successful in many applications throughout the United States. Pumped, or placed, as a low-viscosity liquid, the materials form a strong gel plug in the formation to seal off undesired zones. They are the first materials for this purpose which provide positively-controlled setting times. They have been used to seal off channels in waterfloods, plug thief zones in injection wells, and shut off unwanted water or gas zones in production wells.
The new materials are actually related materials with the same basic formulation, a silicate-acid gel. Use of additives to change strength characteristics of the set gel makes these materials applicable to all types of formations and well conditions. This paper discusses the materials and techniques of placement and describes many of the actual field applications which have proved successful.

Introduction
Many oil or gas wells produce throughout their lives without serious problems arising from undesirable fluid movement. The producing zones in these wells appear to have reasonably uniform permeability distribution, and horizontal permeability much greater than vertical permeability. Unfortunately, these same wells, when converted to injection wells in waterflood projects, may cause problems due to even small variations in permeability distribution. The sections of higher permeability may accept more water and water out, or channel across to a producing well, prematurely. The end result is an inefficient flood with oil still in place that might otherwise have been recovered.
Other formations have poor effective permeability distribution which can create problems during the producing life of a well. Fluid flow through such formations will occur in the zones of highest permeability. As the effective vertical permeability approaches the effective horizontal permeability, cross flow or vertical movement of fluids can cause water or gas coning.
The Petroleum Industry has long recognized the need of a material to control the unwanted movement of fluids through a reservoir. An ideal material should be applicable to both producing and injection wells. The task of providing such a material has been difficult due to wide variations in well and reservoir conditions. It has been further complicated by the very manner in which the permeability exists. The permeability of a rock formation may exist as matrix permeability, as hairline fracture permeability, or as a result of connecting vugs or large pores in the rock. Artificial permeability, such as hydraulically induced fractures, can create unequal permeability distribution. Hydraulic fractures become even more of a problem when they are inclined in a vertical plane.