US-12623162-B2 - System and method for removing drilling fluid from drill cuttings using direct heat

US12623162B2US 12623162 B2US12623162 B2US 12623162B2US-12623162-B2

Abstract

Systems and methods for removing drilling fluid from wet drill cuttings are described. According to some embodiments, the method comprises, at a pressure above atmospheric pressure: combusting a rich air-fuel mixture at a rich combustion temperature, thereby producing a generally low oxygen, inert rich exhaust; providing said rich exhaust to the wet drill cuttings to contact and directly heat the wet drill cuttings by convection so that at least a portion of the drilling fluid is evaporated therefrom and at least some dry solid drill cuttings remain; condensing at least a portion of the evaporated drilling fluid to produce condensed drilling fluid; and separately recovering the condensed drilling fluid and the dry solid drill cuttings.

Inventors

Barry MCINTYRE

Assignees

ELAVO ENERGY SOLUTIONS LTD.

Dates

Publication Date: 20260512
Application Date: 20201118

Claims (17)

1 . A method for removing drilling fluid from wet drill cuttings, comprising: combusting a rich air-fuel mixture at a combustion temperature, thereby producing a generally low oxygen, inert exhaust; providing said exhaust to the wet drill cuttings to contact and directly heat the wet drill cuttings by convection so that at least a portion of the drilling fluid is evaporated therefrom and at least some dry solid drill cuttings remain; agitating the wet drill cuttings while providing the exhaust to the wet drill cuttings; condensing at least a portion of the evaporated drilling fluid to produce condensed drilling fluid; and separately recovering the condensed drilling fluid and the dry solid drill cuttings, wherein providing the exhaust to the wet drill cuttings comprises: (a) providing the exhaust to a fixed bed of a fixed stage configured to receive the exhaust, and (b) providing the exhaust to an agitator stage upstream of and in fluid communication with the fixed bed and configured to receive the exhaust therefrom, the agitator stage having a mechanical mixing device configured to agitate the wet drill cuttings during agitation.
2 . The method of claim 1 , wherein the condensing comprises: recovering heat from the at least the portion of the evaporated drilling fluid.
3 . The method of claim 1 further comprising: at a pressure above atmospheric pressure: prior to the combusting of the rich-air fuel mixture, pre-heating combustion air to a pre-heat temperature lower than the combustion temperature, thereby producing pre-heated combustion air, and adding fuel to the pre-heated combustion air to produce the rich air-fuel mixture.
4 . The method of claim 1 , wherein: the condensing comprises recovering heat from the at least the portion of the evaporated drilling fluid; and the recovered heat is used to pre-heat the combustion air to the pre-heat temperature.
5 . The method of claim 1 further comprising: sensing an oxygen level of the exhaust; and adjusting the amount of fuel or air in the rich air-fuel mixture based on the sensed oxygen level.
6 . The method of claim 1 further comprising: sensing a carbon monoxide level of the exhaust; and adjusting the amount of fuel or air in the rich-air fuel mixture based on the sensed carbon monoxide level.
7 . A system for removing drilling fluid from wet drill cuttings, comprising: a rich combustion chamber having at least one air inlet, at least one fuel inlet, wherein the rich combustion chamber is configured to heat a rich air-fuel mixture at a combustion temperature, thereby producing a generally low oxygen, inert exhaust; a processor having a processing chamber, the processing chamber having a cuttings inlet through which the wet drill cuttings are received into the processing chamber, an evaporated drilling fluids outlet, a dry drilling solids outlet and an exhaust inlet configured to receive the exhaust directly or indirectly from the rich combustion chamber, a fixed stage comprising a fixed bed in fluid communication with the exhaust inlet and configured to receive the exhaust therefrom, an agitator stage upstream of and in fluid communication with the fixed bed and configured to receive the exhaust therefrom, the agitator stage operatively connected to the cuttings inlet and having a mixing device configured to agitate the wet drill cuttings received therefrom, wherein the processor is configured to: provide the exhaust to the processing chamber to contact and directly heat the wet drill cuttings by convection so that at least a portion of drilling fluid is evaporated therefrom and at least some dry solid drill cuttings remain, provide evaporated drilling fluid to the evaporated drilling fluids outlet for recovery therefrom, and provide dry solid drill cuttings to the dry solids outlet for recovery therefrom; and at least one condensing device having a condenser inlet in fluid communication with the evaporated drilling fluids outlet, the at least one condensing device configured to condense at least a portion of the evaporated drilling fluids received directly or indirectly from the evaporated drilling fluids outlet and to provide condensed drilling fluid to a condenser outlet for recovery therefrom; wherein the rich combustion chamber, the processor and the at least one condensing device operate at a pressure above atmospheric pressure; and wherein the providing of the exhaust to the processing chamber to contact and directly heat the wet drill cuttings by convection comprises providing the exhaust to the agitator stage via the fixed bed and agitating the wet drill cuttings by the mixing device.
8 . The system of claim 7 , wherein the at least one condensing device comprises a heat exchanger having at least one heat outlet, the heat exchanger being configured to pre-heat combustion air using heat recovered from the evaporated drilling fluids and to provide the pre-heated combustion air to the rich combustion chamber via the at least one air inlet for combustion, and the system further comprises: a pre-heat combustion chamber having at least one pre-heat air inlet in fluid communication with the at least one heat outlet and configured to receive at least a portion of pre-heated combustion air therein, at least one pre-heat fuel inlet in fluid communication with a fuel source and at least one pre-heat exhaust outlet in fluid communication with the at least one air inlet of the rich combustion chamber; wherein the pre-heat combustion chamber is configured to combust a lean air-fuel mixture comprised of the received pre-heated combustion air at a pre-heated combustion temperature, thereby producing a pre-heated combustion exhaust for receipt by the rich combustion chamber via the at least one air inlet; and wherein the pre-heated combustion temperature is lower than the rich combustion temperature.
9 . The system of claim 7 further comprising: one or more of a exhaust oxygen sensor and a exhaust carbon monoxide sensor, the exhaust oxygen sensor being configured to determine an oxygen level of the exhaust prior to receipt by the processing chamber, and the exhaust carbon monoxide sensor configured to determine a carbon monoxide level of the exhaust prior to receipt by the processing chamber.
10 . The system of claim 9 further comprising a controller operatively connected to the fuel inlet and at least one of the exhaust oxygen sensor and the exhaust carbon monoxide sensor, the controller configured to adjust the fuel-air ratio of the rich fuel-air mixture based on the sensed oxygen level or the sensed carbon monoxide level.
11 . The system of claim 7 further comprising: a heating device configured to heat combustion air and provide heated combustion air to the rich combustion chamber via the at least one air-inlet.
12 . The system of claim 7 further comprising: a natural gas fired engine configured to provide additional air exhaust therefrom directly or indirectly to the processing chamber.
13 . The system of claim 7 further comprising: a natural gas fired engine configured to provide additional air exhaust therefrom directly or indirectly to the processing chamber; wherein the natural gas fired engine provides power to the exhaust heater.
14 . The system of claim 7 , wherein the mixing device is a mechanical mixing device.
15 . The system of claim 7 , further comprising a purge system downstream the fixed stage and configured to compel at least a portion of the dry solid drill cuttings for receipt by the dry solids outlet.
16 . The system of claim 7 , wherein the fixed stage comprises a heat distribution system configured to distribute the received rich exhaust across at least one heat distribution plane of the agitator stage.
17 . A processor for removing drilling fluid from wet drill cuttings, comprising: a processing chamber, the processing chamber having a cuttings inlet through which the wet drill cuttings are received into the processing chamber, an evaporated drilling fluids outlet, a dry drilling solids outlet, a process gas inlet configured to receive process gas, a fixed stage comprising a fixed bed in fluid communication with the process gas inlet and configured to receive the process gas therefrom, an agitator stage upstream of and in fluid communication with the fixed bed and configured to receive the process gas therefrom, the agitator stage operatively connected to the cuttings inlet and having a mixing device configured to agitate the wet drill cuttings received therefrom, wherein the processor is configured to provide the process gas to the fixed bed and the agitator stage, thereby heating the fixed bed and agitator stage so as to heat and agitate the wet drill cuttings so that at least a portion of drilling fluid is evaporated therefrom and at least some dry solid drill cuttings remain, provide evaporated drilling fluid to the evaporated drilling fluids outlet for recovery therefrom, and provide dry solid drill cuttings to the dry solids outlet for recovery therefrom; and wherein the processor operates at a pressure above atmospheric pressure.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS The present application claims priority from U.S. Provisional Patent Application No. 62/939,345 filed on Nov. 22, 2019, the contents of which are incorporated herein by reference. FIELD The specification relates generally to the removal of drilling fluid from wet drill cuttings generated in the drilling of oil and gas wells, and the like, and specifically to methods and systems to remove drilling fluid from wet drill cuttings using thermal techniques. BACKGROUND Drilling for oil and gas produces drill cuttings which are brought to ground surface in the circulating drilling fluid. The drill cuttings may be substantially separated from the drilling fluid using various combinations of shale shakers, centrifuges and mud tanks. However, some liquid or moisture remains associated with the solid “cuttings” as a surface layer and, in some cases, internally thereof. In cases where the drilling fluid is hydrocarbon-based, the cuttings usually are associated with oil, water and drilling fluid chemical additives. Disposal of the wet cuttings is often problematic, as the associated liquids are of environmental concern. These liquids also present problems in handling and treatment. There is a well-known propensity of these cuttings to cake or form unwanted agglomerations when heated and due to mechanical handling and transport operations. This tendency is affected by the amount of liquid present and the nature of the solids and liquids, which can be quite variable. Current methods for disposing of cuttings contaminated with drilling fluid include: hauling the cuttings to a land fill and burying them; composting; bio-remediation; thermal desorption; and combustion. The current methods focus on how to clean up the mess once drilling is terminated, rather than on how to prevent its occurrence in the first place. With most currently used methods, little, if any, of the liquids are recovered, resulting in a loss of drilling fluid. The lost fluid results in increased costs to the drilling operator, including increased disposal costs. Thermal desorption processes are appealing for use in cleaning up cuttings associated with hydrocarbon-based drilling fluids because they can theoretically achieve a zero residual hydrocarbon level. The thermal desorption processes currently used focus on removal of the liquids after drilling is terminated, and usually involve indirect heat. It is commonly believed that using indirect heat to dry the cuttings will reduce the risk of an uncontrolled exothermic reaction between the heated air and the drilling fluids, and that direct heating would require using a heating gas supply that does not support combustion (i.e., a non-combustible heating gas supply). As a result, in processes that use direct heat, friction, rather than heated air, is typically used to generate heat for drying the cuttings (e.g., via hammermill). In addition, current processes that use direct heat are not intended to recover drilling fluid since they usually involve direct heat in conjunction with combustion of the produced drilling fluid vapour. BRIEF DESCRIPTIONS OF THE DRAWINGS For a better understanding of the various implementations described herein and to show more clearly how they may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings in which: FIG. 1A depicts a system for removing drilling fluid from wet drill cuttings, according to a first set of non-limiting embodiments; FIG. 1B depicts a processing chamber of a system for removing drilling fluid from wet drill cuttings, according to non-limiting embodiments; FIG. 2 depicts a system for removing drilling fluid from wet drill cuttings, according to a second set of non-limiting embodiments; FIG. 3 depicts a system for removing drilling fluid from wet drill cuttings, according to a third set of non-limiting embodiments; FIG. 4 depicts a system for removing drilling fluid from wet drill cuttings, according to a fourth set of non-limiting embodiments; FIG. 5 depicts a system for removing drilling fluid from wet drill cuttings, according to a fifth set of non-limiting embodiments; FIGS. 6 to 8 depict a method for removing drilling fluid from wet drill cuttings, according to non-limiting embodiments; FIG. 9 depicts a three-dimensional rendering of a system for removing drilling fluid from wet drill cuttings, according to a non-limiting embodiment; and FIGS. 10A and 10B together depict a piping and instrumentation diagram for a system for removing drilling fluid from wet drill cuttings, according to a non-limiting embodiment. DETAILED DESCRIPTION Herein described are systems and methods for removing drilling fluid from wet drill cuttings. The systems and methods provide practical and efficient means for the drying of drill cuttings generated in the drilling of oil and gas. The wet drill cuttings are directly heated using a low oxygen, generally inert gas at a temperature such that