Wells – Processes – Specific propping feature
Reexamination Certificate
2002-09-05
2004-06-01
Neuder, William (Department: 3672)
Wells
Processes
Specific propping feature
C166S281000, C166S276000
Reexamination Certificate
active
06742590
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to improved methods of treating subterranean formations using solid particles and other larger solid materials.
2. Description of the Prior Art
Hydrocarbon producing subterranean formations penetrated by well bores are often treated by forming gravel packs of solid particles adjacent to the subterranean formation and/or fracturing the subterranean formation and depositing proppant particle packs in the fractures.
In gravel packing operations, solid particles, referred to in the art as gravel, are suspended in water or a viscous fluid at the surface and carried to the well bore in which the gravel pack is to be placed at a designed gravel concentration and pump rate. As the gravel is being placed in the well bore, the carrier fluid is either returned to the surface via the washpipe or leaked off into the formation. The gravel pack produced functions as a filter to separate formation sand and solid fines from produced fluids while permitting the produced fluids to flow into and through the well bore.
Another subterranean formation treatment is hydraulic fracturing. That is, a viscous treating fluid, referred to in the art as a fracturing fluid, is pumped through the well bore into a subterranean formation or zone to be stimulated at a rate and pressure such that fractures are formed and extended into the subterranean formation. The viscous fracturing fluid includes proppant particles, e.g., graded sand, suspended therein which are carried into the fractures. The proppant particles are deposited in the fractures when the viscous fracturing fluid is broken (the viscosity is reduced) and recovered. The proppant particles function to prevent the formed fractures from closing and the closing pressure of the fractures forms the proppant particles into packs. The proppant particle packs maintain the fractures open and form conductive channels through which produced fluids can flow to the well bore.
A problem often experienced in the use of gravel packs and propped fractures is that as formation fluids are produced, the gravel or proppant particles flow-back with the formation fluids. In addition to losing the conductivity of the fractures, the flow-back of the proppant particles with formation fluids is very detrimental in that the resulting solids in the produced formation fluids erode metal goods, plug piping and vessels and cause damage to valves, instruments and other production equipment.
In order to prevent gravel or proppant particle flow-back, other larger solid materials have been combined with the smaller particles in attempts to prevent flow-back. However, a problem encountered with the use of larger solid material with the smaller gravel or proppant particles is that the larger solid material segregates from the smaller particles by floating to the top or settling to the bottom of the carrying fluid. This in turn results in uneven distribution of the smaller particles and larger solid materials which results in the flow-back of both the smaller particles and the larger solid materials with the produced fluids.
Thus, there are needs for improved methods of treating subterranean formations utilizing small solid particles and larger solid materials whereby flow-back of the particles and materials does not occur.
SUMMARY OF THE INVENTION
The present invention provides improved methods of treating subterranean formations using solid particles and other larger solid materials which meet the needs described above and overcome the deficiencies of the prior art. A method of this invention is basically comprised of the following steps. A carrier fluid containing suspended solid particles which have been coated with a non-hardening tackifying compound is introduced into the subterranean formation. A particulate or other shaped solid material of larger size than the solid particles is mixed with the tackifying compound coated smaller solid particles suspended in the carrier fluid whereby the smaller solid particles stick to the larger solid material and the larger solid material is suspended in the carrier fluid along with the smaller solid particles. Thereafter, the larger solid material and the tackifying compound coated smaller solid particles stuck thereto are deposited in the subterranean formation so that upon flowing back fluid from the formation the smaller solid particles and the larger solid material do not flow-back.
The smaller solid particles which are coated with the non-hardening tackifying compound are selected from the group of graded sand, walnut hulls, bauxite, ceramic materials, glass materials and polymer beads. The larger solid material is selected from the group consisting of fibers, shavings, platelets, deformable particles and irregular shaped particulate or pieces.
Another method of this invention for treating a subterranean formation is comprised of the following steps. A viscous fracturing fluid containing suspended solid particles which have been coated with a non-hardening tackifying compound is introduced into fractures formed in the subterranean formation. Deformable particles of a larger size than the proppant particles are mixed with the tackifying compound coated proppant particles suspended in the fracturing fluid whereby the smaller proppant particles stick to the larger deformable particles and the deformable particles are uniformly suspended in the fracturing fluid along with the proppant particles. The deformable particles and the smaller tackifying compound coated proppant particles stuck thereto are deposited in the fractures in the subterranean formation so that upon flowing back fluid from the formation the proppant particles and the deformable particles do not flow-back.
The 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
By the present invention, improved methods of treating subterranean formations using solid particles and other larger solid materials are provided. A method of the invention basically comprises the following steps. A carrier fluid containing suspended solid particles which have been coated with a non-hardening tackifying compound is introduced into a subterranean formation. A particulate or other shaped solid material of larger size than the solid particles are mixed with the tackifying compound coated solid particles suspended in the carrier fluid whereby the smaller solid particles stick to the larger solid material and the larger solid material is uniformly suspended in the carrier fluid along with the solid particles. Thereafter, the larger solid material and the tackifying compound coated solid particles stuck thereto are deposited in the subterranean formation so that upon flowing back fluid from the formation the solid particles and the larger solid material do not flow-back.
The carrier fluid utilized in accordance with this invention is preferably selected from the group consisting of an aqueous gelled liquid, an emulsion, a foamed fluid, a viscoelastic surfactant fluid and water. Of these, an aqueous gelled liquid is preferred. The water utilized in the aqueous gelled liquid can be fresh water or salt water. The term “salt water” is used herein to mean unsaturated salt solutions and saturated salt solutions including brines and seawater. A variety of gelling agents can be included in the carrier fluid to increase the viscosity thereof and suspend the solid particles and larger solid material therein. The gelling agents can be natural and derivatized polysaccharides which are soluble, dispersible or swellable in an aqueous liquid to yield viscosity to the liquid. One group, for example, of polysaccharides which are suitable for use in accordance with the present invention includes galactomannan gums such as guar gum and the like. Modified gums such as carboxyalkyl and hydroxyalkyl derivatives like carboxymethyl guar and hydroxypropyl guar can also be employed.
Dougherty, Jr. C. Clark
Halliburton Energy Service,s Inc.
Kent Robert A.
Neuder William
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