Wells – Processes – Distinct – separate injection and producing wells
Reexamination Certificate
2000-10-26
2002-04-02
Tsay, Frank S. (Department: 3672)
Wells
Processes
Distinct, separate injection and producing wells
C166S270100, C166S300000
Reexamination Certificate
active
06364016
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to methods of reducing the water permeability of water and hydrocarbons producing subterranean formations, and more particularly, to methods of reducing the water produced from such formations without appreciably reducing the hydrocarbons produced therefrom.
2. Description of the Prior Art
Many hydrocarbon wells produce high amounts of water along with the hydrocarbons. For example, eighty percent or more of the total fluids produced can be and often is water. This simultaneous production of water with hydrocarbons constitutes a major expense in the recovery of the hydrocarbons from subterranean producing formations. The expense includes the energy expended in producing the water, and thereafter, separating the water from the produced hydrocarbons and disposing of the water.
A variety of methods and techniques have heretofore been utilized which achieve varying degrees of success in reducing the water permeability of subterranean formations. For example, U.S. Pat. No. 5,146,986 issued to Dalrymple on Sept. 15, 1992 discloses a method of reducing the water produced from a subterranean formation without substantially reducing the oil produced therefrom. In accordance with that method, the formation is contacted with a hydrocarbon treating solution having dissolved therein a surface active agent formed of one or more fatty acid imidazolyl compounds.
Another more recent method of reducing the water permeability of water and hydrocarbons producing formations involves the introduction of a water flow resisting polymer into the formation to reduce the water permeability thereof without substantially reducing the hydrocarbons permeability thereof. While this method has achieved success, a problem which has been encountered is that the polymer can only be injected into the formation a short distance from the well bore. That is, the water flow resisting polymer attaches to adsorption sites on surfaces within the porosity of the formation as it flows from the well bore. Once the polymer is adsorbed onto the surfaces in the formation near the well bore, its presence interferes with and blocks the flow of additional polymer into the formation. This results in limited polymer penetration into the formation and the water producing zone or zones therein which limits the reduction in water production achieved.
Thus, there is a need for improved methods of utilizing water flow resisting polymers to reduce the water permeabilities of producing formations without substantially reducing the hydrocarbons permeabilities thereof.
SUMMARY OF THE INVENTION
The present invention provides improved methods of reducing the water permeability of a subterranean formation without substantially reducing the hydrocarbons permeability which meets the above described need and overcomes the deficiencies of the prior art. In accordance with the improved methods, a chemical which does not resist water flow and attaches to adsorption sites on surfaces within the porosity of the formation but slowly washes off is introduced into the formation. After the chemical has been adsorbed on surfaces within the formation, a water flow resisting polymer is introduced into the formation. As the water flow resisting polymer flows through the formation, it is not initially adsorbed onto the surfaces of the formation due to the presence of the previously adsorbed chemical. As a result, the water flow resisting polymer is pumped from the well bore for long distances into the formation before the chemical washes off the surfaces and allows the polymer to take its place. That is, as the chemical washes off, the water flow resisting polymer is adsorbed onto the formation surfaces resulting in the continuous coating of the formation surfaces from the well bore to long distances away from the well bore.
A preferred method of this invention is comprised of the following steps. A chemical that does not resist water flow, attaches to adsorption sites on surfaces within the porosity of the formation and slowly washes off when another fluid is introduced into the formation is pumped into the formation. A water flow resisting polymer is pumped into the formation so that it flows deeply into the porosity of the formation before the previously adsorbed chemical washes off and the water flow resisting polymer attaches to the adsorption sites as the previously adsorbed chemical washes off. Thereafter, a salt water overflush is pumped into the formation so that excess water flow resisting polymer is displaced more deeply into the formation. Finally, a hydrocarbon liquid (or a gas when a hydrocarbon gas producing zone is being treated) is pumped into the formation to contact the surfaces in the formation.
Thus, it is a general object of the present invention to provide improved methods of reducing the water permeabilities of subterranean water and hydrocarbons producing formations without substantially reducing the hydrocarbon permeabilities thereof.
Other and further objects, features and advantages of the present invention will be readily apparent to those skilled in the art upon a reading of the description of preferred embodiments which follows.
DESCRIPTION OF PREFERRED EMBODIMENTS
The present invention provides improved methods of reducing the water produced from a subterranean formation penetrated by a well bore without substantially reducing hydrocarbons produced therefrom. The improved methods can be utilized in formations formed from various materials such as sandstone, limestone, dolomite and the like and are relatively simple to carry out.
As mentioned, it has recently been found that various water flow resisting polymers can be utilized to reduce the permeabilities of subterranean formations with respect to water without substantially reducing the permeabilities with respect to hydrocarbons. Such polymers which are sometimes referred to as relative permeability modifiers have been dissolved in water and pumped into subterranean formations which produce water and hydrocarbons. The polymers readily attach to adsorption sites on surfaces within the porosities of the formations, but the adsorbed polymers near the well bore interfere with and prevent the polymer from moving very far into the formation. This, in turn, limits the effectiveness of the polymer in reducing the production of water along with hydrocarbons into the well bore.
The improved methods of this invention for treating a water and hydrocarbon liquid and/or gas producing subterranean formation are comprised of the steps of: (a) introducing into said formation a chemical which does not resist water flow and attaches to adsorption sites on surfaces within the porosity of the formation but slowly washes off the sites as another liquid flows through the treated formation, and then (b) introducing into the formation a polymer which functions as a relative permeability modifier, i.e., restricts the water flow through a subterranean formation without substantially reducing the hydrocarbons flow, is introduced into the formation so that it flows deeply into the porosity of the formation before the chemical previously adsorbed washes off and the polymer attaches to the adsorption sites in the formation as the chemical washes off. The methods preferably also include the step of (c) introducing fresh water or salt water, most preferably salt water containing a calcium salt, e.g., 1% to 5% calcium chloride, into the formation after the water flow resisting polymer has been introduced therein whereby excess polymer is displaced more deeply into the formation, and the further step of (d) introducing a hydrocarbon liquid or a gas into the formation to contact the surfaces therein whereby hydrocarbon liquid and/or gas more readily flows through the formation into the well bore.
A variety of chemicals which do not resist water flow, attach to adsorption sites on surfaces within the porosities of subterranean formations and slowly wash off the sites as another fluid flows through the formations can be
Brown David L.
Brown Paul S.
Dalrymple Eldon D.
Eoff Larry S.
Reddy Baireddy R.
Dougherty, Jr. C. Clark
Halliburton Energy Service,s Inc.
Kent Robert A.
Tsay Frank S.
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