Colloid systems and wetting agents; subcombinations thereof; pro – Continuous or semicontinuous solid phase – The solid phase contains organic material
Reexamination Certificate
2000-03-27
2002-10-08
Tucker, Philip (Department: 1712)
Colloid systems and wetting agents; subcombinations thereof; pro
Continuous or semicontinuous solid phase
The solid phase contains organic material
C507S100000, C507S140000, C507S901000, C501S146000
Reexamination Certificate
active
06462096
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to improved oil based well bore fluids known in the oil service industry as drilling fluids, and, in particular, to oil based invert emulsion types of drilling fluids in which water is dispersed in an oil-based medium, which fluids contain defined organoclays. Organoclays are also often referred to as organophilic clay gellants.
In an important aspect the invention relates to novel organophilic clay gellants and to improved oil based drilling fluids containing such organoclays; in still another aspect the invention is directed to processes for providing less temperature dependent viscosity and other rheological properties to such fluids over the wide, and often very high, temperature ranges found in more recent drilling operations.
2. Description of the Prior Art
Oil Well Drilling Fluids
The American oil producing industry has used drilling fluids since the very beginning of oil well drilling operations in the United States. Drilling fluids and their chemistry have been an important area for scientific investigation and contained innovation from the beginning up to the present day.
Such drilling fluids in modern practice are pumped under great pressure through a long “string” of pipe previously placed into the ground after drilling, then (at the very bottom of the drill hole) through the center of the drilling bit, being then returned up through the small space between the outside of the drill pipes and the borehole wall itself. Drilling base fluids, the liquid carriers of the system, are often comprised of oils (diesel, mineral and poly(alpha-olefin)), propylene glycol, methyl glucoside, modified esters and ethers, water, and emulsions of oil and water of varying proportions.
A drilling fluid is a thixotropic system; that is, it exhibits low viscosity when sheared, such as on agitation or circulation (as by pumping) but, when such shearing action is halted, the fluid thickens to hold cuttings in place. The fluid must become thick rapidly, reaching a sufficient gel strength before suspended materials fall any significant distance—and this behavior must be totally reversible at all temperatures encountered. In addition, when a free-flowing liquid, the fluid must retain a sufficiently high viscosity to carry all unwanted particulate matter from the bottom of the hole back up to the surface.
A drilling fluid must accomplish a number of these interrelated functions over a wide range of temperatures to satisfy the requirements to be a commercial drilling fluid. To maintain these functions under the very hot temperatures encountered in modern drilling has proved extremely difficult with the use of commercial rheological drilling fluid additives presently available on the market. These functions can be grouped as follows:
(1) The fluid must constantly lubricate the drill bit so as to promote drilling efficiency and retard bit wear,
(2) The fluid must have a proper thickness or viscosity to meet the many different criteria required by the drill owner/operator,
(3) The fluid must provide filtration control,
(4) The fluid must suspend and transport solid particles such as weighting agents (to increase specific gravity of the mud; generally barytes; a barium sulfate ore, ground to a fine particle size) when drilling is interrupted, and
(5) The fluid must control formation pressure.
The above functions must be satisfactorily provided throughout the time the fluid is in the entire length of the drill hole. Since the drill hole can be as much as tens of thousands of feet long, varying extreme hot and cold temperatures are encountered, which hot temperature changes can particularly affect the fluid's physical properties and performance. Different measures of control during drilling can occur because of high ranges of a) encountered temperature (as high as 250° C.), b) time durations, c) pressures (from only a few bars to those exerted by a column of fluid that can extend for thousands of feet) and d) drilling directions (from vertical to horizontal).
Finally, it should be noted that a drilling fluid must perform its various functions not only when the drill bit is actively encountering the bottom of the borehole, but also at all times and at all locations in the well bore.
One of the principal problems facing “mud chemistry” scientists is the production of thickening agents, thixotropes and drilling fluids having satisfactory dispersibility, with the necessary subsidiary thixotropic properties discussed above, while at the same time possessing critically important rheological properties over a wide range of temperatures. While the compositions of these various fluids is considered a “black art”, in reality, fluids and their additives involve highly complex chemical, and rheological analysis using intricate chemical and mathematical calculations, modeling and rheological analysis.
Accordingly, searches have been going on for many years for improved additives for modifying and controlling the viscosity properties of drilling fluids that would be efficient, easily handled, and readily dispersible in a broad range of drilling muds, and be usable when high temperature are expected to be encountered.
Temperature Sensitivity
In modern times, hydrocarbon drilling for exploratory and production wells has increasingly been done from platforms located in water settings, often called off-shore drilling. Such fresh and salt water drilling employ floating barges and rigs fixed in some fashion to the submerged surface of the earth.
Economic and technical advances have recently pushed these drilling operations into harsher environments. Although advances in equipment and engineering have yielded technology capable of drilling in water depths up to 10,000 feet or more, advances required in drilling fluid technology have lagged.
One important area of application for the new drilling fluid systems is in geothermal drilling, particularly when a well is drilled at an angle other than vertical. The aim of the invention is particularly to make available industrially usable drilling fluids with enhanced properties over a large and “hot” temperature range. The systems can be put to use in land-based drilling operations as well as offshore operations.
Drilling fluids with enhanced temperature properties have become both more important and complex over the past decade as a result of changes in directional drilling technology. Such wells are also known as deviated wells, the extent of the angle of deviation can be from a few degrees to horizontal.
Use of a downhole motor allows the hole to be deviated by the introduction of a fixed offset or bend just above the drill bit. This offset or bend can be oriented by modern MWD systems which are capable of reporting accurately the current bit and toolface hole angle and azimuth (i.e. the orientation with respect to the upper portion of the hole). It is accordingly possible to rotate the drill string until the toolface has achieved the desired direction of deviation, and then to fix the drill string in place and commence the deviation by starting the motor to extend the hole in the desired deviated direction.
Methods for deviating wells have changed greatly over recent years with the production of more powerful and reliable downhole motors, and the invention of more accurate techniques utilizing wireline techniques as well as the highly computerized downhole, sensing and micro reduction equipment, including improvements in sounding apparatus and microwave transmission.
Organoclays
It has been long known that organoclays can be used to thicken organic compositions and particularly drilling fluids. See J. W. Jordan, “Proceedings of the 10
th
National Conference on Clays and Clay Minerals” (1963) which discusses a wide range of applications of organoclays from high polarity liquids to low polarity liquids.
The efficiency of some organophilic clays in non-aqueous systems can be further improved by adding a low molecular weight polar organic material to the composition. Such polar organic mat
Dino David
Thompson Jeffrey
Cronin Michael J.
Elementis Specialties, Inc.
Tucker Philip
LandOfFree
Organophilic clay additives and oil well drilling fluids... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Organophilic clay additives and oil well drilling fluids..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Organophilic clay additives and oil well drilling fluids... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2999634