Additive For Reducing Torque On A Drill String

Abstract

A method of reducing the torque of a drill string used in drilling a subterranean well that includes injecting into the drilling fluid a composition including a base fluid and a polymer coated colloidal solid material. The polymer coated colloidal solid material includes: a solid particle having an weight average particle diameter (d5o) of less than ten microns, and a polymeric dispersing agent coated onto the surface of the solid particle during the cominution (i.e. grinding) process utilized to make the colloidal particles. The polymeric dispersing agent may be a water soluble polymer having a molecular weight of at least 2000 Daltons. The solid particulate material may be selected from materials having of specific gravity of at least 2.68 and preferably the solid particulate material may be selected from barium sulfate (barite), calcium carbonate, dolomite, ilmenite, hematite, olivine, siderite, strontium sulfate, combinations and mixtures of these and other similar solids that should be apparent to one of skill in the art.

Description

BACKGROUND OF THE INVENTION[0001]When oil and gas wells are drilled, fluid formulations with a multitude of properties, including lubricity, are pumped down the well through the drill string and out through nozzles in the drill bit, so that the drilling fluid circulates upward through the annular space between the rotating drill string and the rock formation. The functions of these drilling fluids or “muds” are to cool and lubricate the bit and drill string, to carry the cuttings from the drilling process to the surface, to control and reduce fluid loss into the rock formations, and to support and protect the bore hole until the metal casing can be cemented in place (i.e., create a stable hole).[0002]Mud lubricity (to achieve minimum torque and drag) and mud toxicity (for wells in environmentally sensitive areas, such as offshore drilling) are major concerns when selecting a drilling fluid formulation. Most drilling fluids may be grouped into two major categories: water-based or ole...

AI Technical Summary

Benefits of technology

[0006]The present invention is generally directed to fluids useful in reducing the torque of drill string, as well as methods for making and methods of using such fluids. The fluids of the present inve

Problems solved by technology

Although oleaginous-based drilling fluids including the so-called synthetic-based fluids do have performance advantages, drawbacks are higher costs and difficult environmental compliance in specific areas of the world.

These lubricants can increase the toxicity and irritation level of the fluids.

Common difficulties with the above solid lubricants have been the environmental concerns when aqueous based drilling fluids are being used and the loading up of the drilling fluid with solid materials.

Further, it should be appreciated that the addition of solid materials that do not contribute to the weighting of the fluid may result in an underweight fluid raising concerns about blow-out or wall collapse.

A further problem encountered with solid lubricating agents is small diameter apertures present in the valves and other flow and pressure control equipment used may prevent the use of solid particulate lubricating agents because these material block and plug the narrow restrictions.

A more serious concern is that the solids might be difficult to remove from the well bore and thus cause formation damage.

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