|Publication number||USH1685 H|
|Application number||US 08/499,156|
|Publication date||Oct 7, 1997|
|Filing date||Jul 7, 1995|
|Priority date||Jul 7, 1995|
|Publication number||08499156, 499156, US H1685 H, US H1685H, US-H-H1685, USH1685 H, USH1685H|
|Inventors||Hon Chung Lau, Arthur Herman Hale, Louis Anthony Bernardi, Jr.|
|Original Assignee||Shell Oil Company|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (7), Referenced by (11), Classifications (7), Legal Events (1)|
|External Links: USPTO, USPTO Assignment, Espacenet|
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.
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.
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.
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US3622513 *||May 10, 1968||Nov 23, 1971||Oil Base||Oil base fluid composition|
|US5072794 *||Mar 19, 1991||Dec 17, 1991||Shell Oil Company||Alcohol-in-oil drilling fluid system|
|US5301754 *||Oct 22, 1992||Apr 12, 1994||Shell Oil Company||Wellbore cementing with ionomer-blast furnace slag system|
|US5307877 *||Oct 22, 1992||May 3, 1994||Shell Oil Company||Wellbore sealing with two-component ionomeric system|
|US5332040 *||Oct 22, 1992||Jul 26, 1994||Shell Oil Company||Process to cement a casing in a wellbore|
|US5343952 *||Oct 22, 1992||Sep 6, 1994||Shell Oil Company||Cement plug for well abandonment|
|US5363918 *||Aug 4, 1993||Nov 15, 1994||Shell Oil Company||Wellbore sealing with unsaturated monomer system|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US6790812||Nov 30, 2001||Sep 14, 2004||Baker Hughes Incorporated||Acid soluble, high fluid loss pill for lost circulation|
|US6968898 *||Jun 28, 2002||Nov 29, 2005||Halliburton Energy Services, Inc.||System and method for removing particles from a well bore penetrating a possible producing formation|
|US7169738||Jun 3, 2005||Jan 30, 2007||M-I L.L.C.||Method of using a sized barite as a weighting agent for drilling fluids|
|US7176165||Jun 3, 2005||Feb 13, 2007||M-I L.L.C.||Method of drilling using a sized barite as a weighting agent for drilling fluids|
|US7220707||Jun 3, 2005||May 22, 2007||M-I L.L.C.||Sized barite as a weighting agent for drilling fluids|
|US7409994||Dec 28, 2006||Aug 12, 2008||M-I L.L.C.||Drilling well with drilling fluid of fluid phase and weighting agent|
|US7825075 *||Jun 9, 2009||Nov 2, 2010||Baker Hughes Incorporated||Viscosity enhancers for viscoelastic surfactant stimulation fluids|
|US7918289 *||Jun 22, 2007||Apr 5, 2011||M-I L.L.C.||Method of completing a well with sand screens|
|US8168569||Sep 11, 2007||May 1, 2012||M-I L.L.C.||Precipitated weighting agents for use in wellbore fluids|
|US20040000434 *||Jun 28, 2002||Jan 1, 2004||Todd Bradley L.||System and method for removing particles from a well bore penetrating a possible producing formation|
|US20090312203 *||Dec 17, 2009||Baker Hughes Incorporated||Viscosity enhancers for viscoelastic surfactant stimulation fluids|
|International Classification||C09K8/32, C09K8/16|
|Cooperative Classification||C09K8/16, C09K8/32|
|European Classification||C09K8/32, C09K8/16|
|Jun 9, 1997||AS||Assignment|
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