Bp Corporation North America Inc.

Bp Exploration Operating Company Limited

The Queen's University of Belfast

Mark Shelton Aston

Kenneth Richard Seddon

Christopher Alan Sawdon

Mark William Alberty

Randall Vashishta Sant

David Wassell

Ian Gray

Mark E Sanders

Jim Friedheim

Dana Aytkhozhina

Jianguo Zhang

Michael Richard Mclean

Juan Carlos Rojas

David Francis Wassell

Mary Ann George

The invention provides a wellbore fluid which comprises an aqueous continuous phase and, dissolved in said aqueous continuous phase, at least one salt containing an imidazolium cation having at least 6 carbon atoms, and a method of carrying out a wellbore operation, which comprises introducing into a wellbore in a clay-containing formation, a wellbore fluid according to the invention. The described salts are effective shale inhibitors.

Aqueous-based wellbore fluids

The invention provides a wellbore fluid which comprises an aqueous continuous phase and, dissolved in said aqueous continuous phase, at least one salt which exists in a liquid state at a temperature below 150&#xb0; C. and which has an ammonium, phosphonium or sulfonium cation containing at least 5 carbon atoms, or a quaternised nitrogen-containing heterocyclic cation containing at least 6 carbon atoms; provided that said salt is not 2-hydroxy-N,N,N-trimethyl ethanaminium acetate; and a method of carrying out a wellbore operation, which comprises introducing into a wellbore in a clay-containing formation, a wellbore fluid according to the invention. The described salts are effective shale inhibitors.

A method of increasing the fracture resistance of a low permeability formation that includes emplacing a wellbore fluid in a wellbore through the low permeability formation, the wellbore fluid comprising: a settable carrier fluid; and a solid particulate bridging material; increasing the pressure in the wellbore such that fractures are formed in the formation; allowing the settable carrier fluid to enter the fractures; bridging and sealing the mouths of the fractures to form a substantially impermeable bridge proximate the mouth of the fractures thereby strengthening the formation; and holding the increased pressure for an amount of time sufficient for setting of the carrier fluid in the fractures is disclosed.

Methods of increasing fracture resistance in low permeability formations

In accordance with aspects of the present disclosure, techniques for predicting, classifying, preventing, and remedying drilling fluid circulation loss events are disclosed. Tools for gathering relevant data are disclosed, and techniques for interpreting the resultant data as giving rise to an actual or potential drilling fluid lost circulation event are also disclosed.

Prediction and diagnosis of lost circulation in wells

Method of consolidating sand in a subterranean formation by contacting the sand in a first location in the presence of water with a slurry in a liquid medium of cement of average particle size less than 10 microns to produce a mixture including sand, water and cement, the slurry being injected into the formation to the location. A separation step is carried out in which a liquid hydrocarbon fluid is passed into the location to displace from the location at least some of the cement from the mixture. The volume ratio of liquid hydrocarbon fluid to the volume of the slurry injected to the formation is at least 5:1. The mixture is allowed to set to give permeable consolidated sand.

Formation treatment

Method of treating a subterranean hydrocarbon-bearing formation comprising unconsolidated or poorly consolidated particulates, by contacting the formation with a solution or a dispersion of an organosilane which is a silylated polymer of formula (I):(RO)RSi-A-B-A-Si(OR)R&#x2003;&#x2003;(I)

Process for consolidating sand

A method of reducing formation breakdown during the drilling of a wellbore which method comprises: (a) circulating a drilling mud in the wellbore comprising (i) an aqueous or oil based fluid, (ii) at least one fluid loss additive at a concentration effective to achieve a high temperature high pressure (HTHP) fluid loss from the drilling mud of less than 2 ml/30 minutes and (iii) a solid particulate bridging material having an average particle diameter of 25 to 2000 microns and a concentration of at least 0.5 pounds per barrel; (b) increasing the pressure in the wellbore to above the initial fracture pressure of the formation such that fractures are induced in the formation and a substantially fluid impermeable bridge comprising the solid particulate bridging material and the fluid loss additive(s) is formed at or near the mouth of the fractures thereby strengthening the formation; (c) thereafter continuing to drill the wellbore with the pressure in the wellbore maintained at above the initial fracture pressure of the formation and below the breakdown pressure of the strengthened formation.

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Middlesex, United Kingdom

Mark Shelton Aston