A New Water-Oil Ratio Improvement Material (1978)

Abstract A new water-oil ratio improvement chemical has been developed which, when applied to producing wells, may substantially improve profitability by decreasing water production and permitting additional oil to be produced. The material, which is polymeric, has a different conformation and polymeric, has a different conformation and polymer-rock interaction than previously used polymer-rock interaction than previously used materials. This new polymeric Water-Oil Ratio Control Agent will be referred to as WORCA which is an acronym for use in this paper only. The performance of WORCA is not significantly altered by performance of WORCA is not significantly altered by mechanical shear, exposure to oxygen, acids, oils, or other normally encountered oil field fluids. Laboratory results show a significant decrease in relative permeability to water after the WORCA has been applied to a simulated producing formation. Consequent movement of oil relative to that of water is improved. These tests also indicate that wash off is minimal after the material is placed. placed. Application to a producing well is quite simple. An aqueous dilution of the base material is introduced into the formation at less than fracturing pressure. Normally, a rig is not required. No waiting or down-time is necessary. The well may be returned to production immediately. Developmental field applications have been very encouraging. There has been either (1) marked decrease in water production, (2) a lowered fluid level while pumping the well, (3) an increase in oil production or (4) all of these. Introduction Water production from oil wells is almost unavoidable in water drive reservoirs. The industry traditionally has lived with this problem by either separating and disposing of the produced water or by squeezing with a plugging agent to restrict water entry. The introduction of strict governmental regulations to control the disposal of produced water has rapidly increased the cost of handling this water. For example, in one field, the cost to lift, separate, and dispose of the produced water is $.15 per barrel. The encroachment of water usually causes a significant decrease in oil production. Normally, as the degree of water saturation increases, the relative oil premeability is reduced. In many cases, the relative oil permeability of a typical sandstone formation approaches 0 when the degree of water saturation is greater than about 40–60%. A high degree of water saturation near the wellbore may be due to water coning, water fingering, communication with a water zone through high permeability streaks, fissures and/or fractures. As the degree of water saturation increases, water is produced instead of oil. This water may actually "kill" the oil producing zones or portions of zones which are in the same completion. The high production rate of water may have other problems associated with it, e.g., increased corrosion, sand production, emulsion formation, disposal, etc. Historically there have been two general methods of treating undesired water production. If the region of water production is well defined and can be isolated, the treatment of that region only with a material which will "set-up" to irreversibly plug the matrix is the preferred method. Examples of zone isolation methods are cement squeezes and acrylamide and sodium silicate type grouts. These methods are generally expensive because of the equipment required. In the event of a poorly defined water entry or when the expense of a rig is not justified, the use of a variety of chemicals to selectively reduce water production has been attempted. Some of these methods involve dispersing materials in an oil base fluid.