Earth boring – well treating – and oil field chemistry – Well treating – Contains organic component
Reexamination Certificate
2001-02-23
2003-01-28
Tucker, Philip (Department: 1712)
Earth boring, well treating, and oil field chemistry
Well treating
Contains organic component
C507S271000, C507S922000, C166S308400, C558S214000
Reexamination Certificate
active
06511944
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to gelled liquid hydrocarbon fluids and methods of their use and preparation.
2. Description of the Prior Art
High viscosity gelled hydrocarbon liquids have heretofore been utilized in treating subterranean formations penetrated by well bores, e.g., hydraulic fracturing stimulation treatments. In such treatments, a high viscosity gelled liquid hydrocarbon fracturing fluid having particulate proppant material, e.g., sand, suspended therein is pumped through a well bore into a subterranean formation to be stimulated at a rate and pressure such that one or more fractures are formed and extended in the formation. The suspended proppant material is deposited in the fractures when the gelled hydrocarbon fracturing fluid is broken and returned to the surface. The proppant material functions to prevent the formed fractures from closing whereby conductive channels remain through which produced fluids can readily flow to the well bore.
Polyvalent metal salts of orthophosphoric acid esters have heretofore been utilized as gelling agents for forming high viscosity gelled liquid hydrocarbon fracturing fluids. Such gelled liquid hydrocarbon fracturing fluids have included fracture proppant material and delayed breakers for causing the fracturing fluids to break into relatively thin fluids whereby the proppant material is deposited in formed fractures and the fracturing fluid is produced back. Descriptions of such heretofore utilized high viscosity gelled liquid hydrocarbon fracturing fluids and methods of their use are set forth in U.S. Pat. No. 4,622,155 issued to Harris et al. on Nov. 11, 1986, and U.S. Pat. No. 5,846,915 issued to Smith et al. on Dec. 8, 1998. The gelled liquid hydrocarbon fracturing fluids described in the above patents utilize ferric iron or aluminum polyvalent metal salts of phosphoric acid esters as gelling agents and delayed breakers such as hard burned magnesium oxide which is slowly soluble in water.
While the heretofore utilized high viscosity gelled liquid hydrocarbon fracturing fluids and methods have been used successfully for forming fractures in subterranean formations, problems have been encountered as a result of the use of the gelling agent, i.e., the polyvalent metal salt of a phosphoric acid ester. That is, in recent years plugging of refinery towers which process oil produced from formations fractured with gelled liquid hydrocarbon fracturing fluids has caused many expensive, unplanned shut-downs. The plugging material is high in phosphorus and has been attributed to the phosphate esters used as gelling agents. The phosphate esters contribute volatile phosphorus which condenses on distillation tower trays, causing plugging. The volatile phosphorus may also carry over the tops of the distillation towers causing contamination of the hydrocarbon products produced.
Thus, there are needs for improved methods of using and preparing gelled liquid hydrocarbons which upon breaking and being refined substantially reduce volatile phosphorus in distillation towers, improved liquid hydrocarbon gelling agents and improved gelled liquid hydrocarbon compositions. More specifically, in fracturing oil producing subterranean formations in areas where volatile phosphorus is a problem in refineries, there is a need to reduce the production of volatile phosphorus in the refineries to levels where the above described unscheduled refinery shut downs are not required without compromising CO
2
compatibility with the gelled oil fracturing fluids used. Concentrations of CO
2
as high as 40-50% are commonly used in gelled oil fracturing fluids which form miscible mixtures with the fluids. The presence of the CO
2
enhances fluid recovery, minimizes the amount of oil based fracturing fluid which must be recovered, and reduces costs in areas where CO
2
is less expensive than the oil based fracturing fluid.
SUMMARY OF THE INVENTION
The present invention provides improved methods of using and preparing gelled liquid hydrocarbons, improved liquid hydrocarbon gelling agents and improved gelled liquid hydrocarbon compositions which meet the above described needs and overcome the deficiencies of the prior art.
The improved methods of this invention for fracturing subterranean formations using gelled liquid hydrocarbons are basically comprised of the following steps. An improved gelled liquid hydrocarbon fracturing fluid is prepared comprised of a hydrocarbon liquid, a gelling agent comprised of a ferric iron or aluminum polyvalent metal salt of a phosphonic acid ester, a proppant material, water and an amount of a delayed gel breaker effective to break the gelled hydrocarbon fracturing fluid. The phosphonic acid ester utilized in the gelling agent which minimizes volatile phosphorus in refinery distillation towers has the formula
wherein R is an alkyl group having from about 8 to about 24 carbon atoms and R′ is an alkyl group having from about 1 to about 4 carbon atoms. After the gelled liquid hydrocarbon fracturing fluid is prepared, the subterranean formation to be fractured is contacted with the gelled liquid hydrocarbon fracturing fluid under conditions effective to create at least one fracture in the subterranean formation.
The improved methods of this invention for preparing gelled liquid hydrocarbons basically comprise adding a phosphonic acid ester having the formula
wherein R is an alkyl group having from about 8 to about 24 carbon atoms and R′ is an alkyl group having from about 1 to about 4 carbon atoms, and preferably, at least a stoichiometric amount of a polyvalent metal source selected from ferric iron salts and aluminum compounds to a hydrocarbon liquid. The polyvalent metal source reacts with the phosphonic acid ester to form a ferric iron or aluminum polyvalent metal salt thereof. Water and an amount of a delayed gel breaker effective to break the gelled liquid hydrocarbon fracturing fluid is also added to the hydrocarbon liquid.
The improved liquid hydrocarbon gelling agents of this invention are comprised of a ferric iron or aluminum polyvalent metal salt of a phosphonic acid ester, the phosphonic acid ester having the formula
wherein R is an alkyl group having from about 8 to about 24 carbon atoms and R′ is an alkyl group having from about 1 to about 4 carbon atoms.
The improved gelled liquid hydrocarbon compositions of this invention are comprised of a hydrocarbon liquid, a gelling agent comprising a polyvalent metal salt of a phosphonic acid ester produced from a phosphonic acid ester and a ferric iron salt or an aluminum compound, the phosphonic acid ester having the formula
wherein R is an alkyl group having from about 8 to about 24 carbon atoms and R′ is an alkyl group having from about 1 to about 4 carbon atoms, water and a delayed gel breaker present in an amount effective to break the gel formed by the gelling agent and the hydrocarbon liquid.
It is, therefore, an object of the present invention to provide improved methods and compositions useful in treating subterranean formations as well as in other similar applications.
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 methods of treating subterranean formations penetrated by well bores with gelled liquid hydrocarbon fluids. For example, the gelled liquid hydrocarbon fluids are suitable for use in fracturing treatments carried out in subterranean formations whereby the production of hydrocarbons from the subterranean formations is stimulated. In accordance with the present invention, a fracturing fluid comprised of a gelled liquid hydrocarbon or mixture of hydrocarbons containing a proppant material and a delayed gel breaker is pumped through a well bore into a subterranean formation to be stimulated. The fracturing fluid is pumped at a rate and pressure such that one or more fracture
Funkhouser Gary P.
Taylor Robert S.
Dougherty, Jr. C. Clark
Halliburton Energy Service,s Inc.
Kent Robert A.
Tucker Philip
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