Control of Sand Production in the Underground Storage of Natural Gas

Abstract

Production of sand during withdrawal of gas from a storage field can cause Production of sand during withdrawal of gas from a storage field can cause reservoir damage, loss of deliverability and damage to subsurface tubular goods and to surface equipment. It can even jeopardize the safety of personnel by causing fires and blow-outs. Sand consolidation helped to personnel by causing fires and blow-outs. Sand consolidation helped to reduce these problems in the Redfield and Vincent storage fields in Iowa. Introduction Gas storage wells completed in unconsolidated or poorly consolidated sandstone aquifers have presented a problem to the underground gas storage industry for many years. Of primary concern is the production of sand during a withdrawal season, and the inherent problems it causes such as blow-outs and fires, eroded surface and subsurface equipment and reservoir damage. Sand production hampers the development of new storage fields because it makes it impossible to secure adequate water pumping data for caprock and aquifer evaluation. Initially, sand screens and slotted liners for controlling sand production were evaluated, but the liners either plugged or had holes eroded in them by the sand. The slotted liners allowed too much sand to be produced and had to be removed when the wells needed stimulating and cleaning out. Therefore, the method of plastic sand consolidation was investigated. The low bottom-hole temperature of about 60F in the aquifers presented a problem because the resin used in the oil fields presented a problem because the resin used in the oil fields was designed for higher temperatures. Thus it was necessary to develop an ultra-low-temperature consolidation system for the 60 to 90F range. The patented three-step process that was adopted produces the desired properties in a resin-consolidated formation, i.e., high compressive strength and retained permeability. Although the desired characteristics have been attained, there are a few disadvantages to all plastic sand consolidation methods, such as high costs and the difficulty of controlling placement of chemicals in the reservoir. placement of chemicals in the reservoir. Presented here are some of the parameters that were considered in developing a satisfactory injection system for plastic sand consolidation and an evaluation of wells consolidated plastic sand consolidation and an evaluation of wells consolidated by this process. The Process of Sand Consolidation During the sand consolidation process each sand grain is coated with an epoxy resin so that pendular rings of the resin harden to form a connecting bond for the sand grains. The consolidation treatment consists of five basic steps:pumping a diesel preflush into the formation to reduce the water saturation to a preflush into the formation to reduce the water saturation to a minimum,pumping acetone into the formation to remove the remaining water saturation,pumping the epoxy resin containing a patented additive that increases the resin's affinity for the sand grains,pumping a diesel solution into the formation to displace the excess epoxy resin from the pore channels to re-establish permeability, andpumping a diesel-activator mixture to polymerize the resin in the form of pendular rings bonding the sand grains. JPT P. 581