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Publication numberUSH1685 H
Publication typeGrant
Application numberUS 08/499,156
Publication dateOct 7, 1997
Filing dateJul 7, 1995
Priority dateJul 7, 1995
Publication number08499156, 499156, US H1685 H, US H1685H, US-H-H1685, USH1685 H, USH1685H
InventorsHon Chung Lau, Arthur Herman Hale, Louis Anthony Bernardi, Jr.
Original AssigneeShell Oil Company
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Consists of liquid carrier medium and weighing agent of zinc oxide or zirconium oxide having particle size range of 4 to 200 microns, used in geopressurized horizontal wells
US H1685 H
Abstract
Zinc oxide and zirconium oxide are used as weighting materials for water and oil based drilling fluids for horizontal wells.
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Claims(5)
We claim:
1. A drilling fluid for use in geopressured horizontal wells comprising a liquid carrier medium and a weighting agent of zinc oxide or zirconium oxide having a particle size range of 4 to 200 microns.
2. The drilling fluid of claim 1 wherein the particle size range is 6 to 100 microns.
3. The drilling fluid of claim 1 wherein the particle size range is 8 to 50 microns.
4. The drilling fluid of claim 1 wherein the liquid carrier medium is water base.
5. The drilling fluid of claim 1 wherein the liquid carrier medium is oil base.
Description
BACKGROUND

The present invention relates to drilling fluids of the type employed in oil and gas wells. More particularly, the invention relates to weighting materials for water and oil based drilling fluids for horizontal wells.

In drilling geopressured horizontal wells, a drilling fluid with density between 12-19 ppg is often required. Traditionally, barite (barium sulfate) is used as weighting material for drilling fluid. Barite is not suitable for horizontal wells because a barite-laden filtercake cannot be dissolved. Undissolved barite particles can invade the production screen in the horizontal well and plug it causing cessation or reduction in flow of hydrocarbon.

The present invention in response to this need in the art provides a solution as described hereinafter.

SUMMARY

The primary purpose of the present invention is to alleviate problems with weighting materials in drilling muds used in drilling geopressured horizontal wells. To this end, zinc oxide and zirconium oxide are used as weighting agents in such drilling fluids, preferably in particle sizes of the order of 10 microns or a range of 4 to 200 microns.

PREFERRED EMBODIMENTS

Zinc oxide is a particularly suitable material for weighting because, it has a high density (5.6 g/ml versus 4.5 for barite); It is soluble in acids (e.g. HCl); and its particle size can be designed so that it does not invade the formation. Acid solubility is particularly desirable because dissolved ZnO can be produced through a production screen without plugging it. A high density means less weighting material is needed per unit mud volume to achieve a desired density. Tests were performed with commercially available ZnO particles. Surprisingly, it was found that the particle size (of the order of 10 microns) is such that the ZnO particles do not invade the formation core with the filtrate. Also it is not large enough to settle out of suspension. Other weighting material such as manganese tetraoxide is so fine that it invades the formation with the filtrate. Zirconium oxide possesses similar properties as ZnO. It has a density of 5.7 and is soluble in nitric acid and hot concentrated hydrochloric, hydrofluoric and sulfuric acids, making it useful in the invention.

As above observed, these materials are acid soluble. Hence filtercake formed from them can be dissolved and produced through the production screen without plugging it. Also they are fine enough to be easily suspended in the oil or water base mud, but not too fine to invade the formation with the filtrate. The very high acid solubility of ZnO makes it particularly suitable as weighting material. This problem is unique to horizontal wells because they are often completed as open holes without a casing. A production screen is placed in the open hole to retain sand and yet allow hydrocarbon to be produced.

Solubility of ZnO in HCl at elevated temperatures was measured. At 150 F., solubility of ZnO in 15% w/v HCl is 60 lb/bbl and 98 lb/bbl in 25% w/v HCl. Return permeability experiments with ZnO weighted waterbase mud showed that the ZnO mud did not damage the formation and that the ZnO filtercake can be dissolved by HCl. Experiments also showed that an aqueous NaBr mud weighted with ZnO has acceptable rheology for drilling.

As above-mentioned, particle size is extremely important to the invention. U.S. Pat. No. 3,622,513 to George Miller, patented Nov. 23, 1961, incorporated hereinto by reference thereto, discloses the use of zinc oxide in an oil base mud as a weighting agent. However, Miller uses very small particle sizes of less than 3 microns. This would not be suitable for use with the present invention. The size of the particles of this invention is such that it does not invade the formation core with the filtrate and it is not large enough to settle out of suspension. Accordingly, the present invention is useful with a particle size range of 4 to 200 microns, more preferably 6 to 100, and most preferably 8 to 50.

The present invention is suitable for use with all types of muds, both water base and oil base, as well as emulsion muds, including invert emulsion muds and synthetic muds. The invention is suitable for use with the alcohol-in-oil drilling fluid described in U.S. Pat. No. 5,072,794 to Hale et al, issued Dec. 17, 1991, which disclosure is incorporated hereinto by reference thereto. The oil can be vegetable or mineral or can be synthetic such as esters, isomerized olefins or polyalpha olefins. For water base muds the water can be fresh, brackish or brine.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US3622513 *May 10, 1968Nov 23, 1971Oil BaseOil base fluid composition
US5072794 *Mar 19, 1991Dec 17, 1991Shell Oil CompanyAlcohol-in-oil drilling fluid system
US5301754 *Oct 22, 1992Apr 12, 1994Shell Oil CompanyWellbore cementing with ionomer-blast furnace slag system
US5307877 *Oct 22, 1992May 3, 1994Shell Oil CompanyUsing a water soluble polymer
US5332040 *Oct 22, 1992Jul 26, 1994Shell Oil CompanyProcess to cement a casing in a wellbore
US5343952 *Oct 22, 1992Sep 6, 1994Shell Oil CompanyCement plug for well abandonment
US5363918 *Aug 4, 1993Nov 15, 1994Shell Oil CompanyCombining drilling fluid consists of metal oxide and water with polymerizable monomer in presence of peroxide to form cementitious slurry to cement the well
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US6790812Nov 30, 2001Sep 14, 2004Baker Hughes IncorporatedSpotting pill/slug containing a lost circulation material consisting of an acid soluble mineral particulate adapted to form an impermeable, acid soluble filtercake upon injection of with said carrier fluid into wellbore and defluidization.
US6968898 *Jun 28, 2002Nov 29, 2005Halliburton Energy Services, Inc.Drilling fluid is mixed with a weighted material, and the mixture is introduced into a well bore so that the mixture scours any particles accumulated in well bore; well-completion fluid is introduced into well bore that dissolves weighted material
US7169738Jun 3, 2005Jan 30, 2007M-I L.L.C.Method of using a sized barite as a weighting agent for drilling fluids
US7176165Jun 3, 2005Feb 13, 2007M-I L.L.C.Solid phase weight material selected from barite, calcite, hematite, ilmenite; fluid phase is an oleaginous fluid selected from diesel oil, mineral oil, or synthetic oil
US7220707Jun 3, 2005May 22, 2007M-I L.L.C.Sized barite as a weighting agent for drilling fluids
US7409994Dec 28, 2006Aug 12, 2008M-I L.L.C.Circulating a drilling fluid containing solid phase weight material selected from barite, calcite, hematite, ilmenite; fluid phase is an oleaginous fluid selected from diesel oil, mineral oil, or synthetic oil; has rheological properties comparable to a conventional wellbore fluid
US7825075 *Jun 9, 2009Nov 2, 2010Baker Hughes IncorporatedReducing fluid leakoff during a fracturing operation by injection into a well bore a viscoelastic surfactant gelling agent and pyroelectric particles, piezoelctric particles and mixtures which under pressure and heating increase gelation to provide a high viscosity fluid for cracking
US7918289 *Jun 22, 2007Apr 5, 2011M-I L.L.C.Method of completing a well with sand screens
US8168569Sep 11, 2007May 1, 2012M-I L.L.C.Precipitated weighting agents for use in wellbore fluids
Classifications
U.S. Classification507/140
International ClassificationC09K8/32, C09K8/16
Cooperative ClassificationC09K8/16, C09K8/32
European ClassificationC09K8/32, C09K8/16
Legal Events
DateCodeEventDescription
Jun 9, 1997ASAssignment
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:LAU, HON CHOUNG;HALE, ARTHUR HERMAN;BERNARDI, LOUIS ANTHONY JR.;REEL/FRAME:008566/0214
Effective date: 19950703
Owner name: SHELL OIL COMPANY, TEXAS