Apparatus and method for recovering oil-based drilling mud

Abstract

Oil-based drilling fluid is prepared for further processing to recover the drilling fluid by pumping the drilling fluid through a flow meter. Surfactant may be added to the drilling fluid by using a dose pump and a flow meter. The drilling fluid and surfactant are then blended by passing them through a static mixer. A flocculating polymer is transferred via dose pumps to another static mixer where it is blended with the surfactant and drilling fluid mixture. To ensure adequate mixing and reaction, additional mixers are included through which the mixture passes. A centrifuge is used to separate solid particles from the fluid.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]The present application is a divisional application of U.S. patent application Ser. No. 11 / 300,640, filed on Dec. 15, 2005 which claims priority to U.S. Provisional Application Ser. No. 60 / 670,528, filed Apr. 11, 2005 and which is a continuation-in-part of U.S. patent application Ser. No. 11 / 102,952 filed on Apr. 11, 2005, the subject matter of all three related applications hereby incorporated by reference.BACKGROUND OF INVENTION[0002]In the process of rotary drilling a well, drilling fluid, or mud, is circulated down the rotating drill pipe, through the bit, and up the annular space between the pipe and the formation or steel casing, to the surface. The drilling fluid performs different functions such as removal of cuttings from the bottom of the hole to the surface, to suspend cuttings and weighting material when the circulation is interrupted, control subsurface pressure, isolate the fluids from the formation by providing sufficient h...

AI Technical Summary

Benefits of technology

[0012]The flocculant mixture is added to the drilling fluid mixture and further mixing occurs through a series of additional mixers. Upon exiting the final mixer, the drilling fluid mixture is prepared to have solids separated therefrom so that the oil-based drilling fluid may be further processed for recovery. A centrifuge receives the drilling fluid mixture from the final mixer. A steam generator injects steam into the drilling fluid mixture immediately prior to the inlet of the centrifuge. The steam and drilling fluid mixture are received into the centrifuge, which is rotated at a speed sufficient to remove solids from the drilling fluid. The addition of steam to the drill fluid mixture prior to centrifugation enhances the ability of the centrifuge to remove the low gravity solids that are entrained within the drilling fluid. The solids, including low gravity solids are directed to a cuttings box while the effluent from the centrifuge is directed to a holding tank or to additional processing equipment to prepare the fluid for re-use as drilling fluid.

[0013]In another illustrated aspect, a method for preparing oil based drilling fluid for recovery is claimed. The method includes demulsifying the drilling fluid with a surfactant and preparing a flocculant mixture. The flocculant mixture is then mixed with the drilling fluid mixture. The next step includes separating solids from the drilling fluid mixture and collecting them. The method includes directing effluent from the separating solids step to a centrifuge that is operational to reduce the percentage of solids from the effluent to less than 10%. Steam is injected into the drilling fluid immediately prior to being injected into the centrifuge. The centrifuge is operated under normal operating conditions. The injected steam enhances the effectiveness of the centrifuge such that the effluent includes less than 5.5% solids. Further, the solids in the effluent include less than 1.5% low gravity solids. As the process is allowed to continue, the amount of low gravity solids remaining in the effluent is lowered to zero.

Problems solved by technology

Unless these are removed, they eventually alter the fluid's properties, particularly the rheological parameters, out of the acceptable range.

However, formation particles that are less than about 5 to 7 μm in size are more difficult to remove than larger particles.

These low gravity solids can build up in a mud system, causing inefficient drilling problems such as drill pipe sticking, increased pipe torque, and other high viscosity issues.

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