ROTATIONAL FLOW ROTATION DEOILING METHOD AND DEVICE FOR OIL-BASED MUD ROCK DEBRIS

Abstract

Disclosed is a rotational flow rotation deoiling method for oil-based mud rock debris. The method comprises the following steps: (1) System viscosity control, wherein by means of heat exchange between a gas medium and the rock debris, the viscosity of the oil-based mud debris is reduced to reduce the interaction force between oil, water, and the surface and channels of solid particles, thereby facilitating the separation in a rotational flow field; (2) Rotational flow rotation deoiling, wherein the oil-based mud rock debris particles undergo a coupled motion of rotation and revolution, wherein by means of the rotation of the rock debris particles, the centrifugal desorption of oil on the surface of a solid phase, oil in capillaries and oil in pores is enhanced; and by means of the centrifugal force of periodic oscillation generated by the revolution thereof, the separation and enrichment of oil and gas and the solid phase are completed, thereby achieving the removal of the oil phase from the pore channels of the rock debris; and (3) gas-liquid separation and reuse, wherein an oil-containing mixture produced in step (2) is subjected to gas-liquid separation so as to realize the reuse of a base oil, circulation of the gas medium, and a harmless treatment of the rock debris; and a rotational flow rotation deoiling device for oil-based mud rock debris is further comprised.

Claims

1. A method for deoiling of oil-based mud cuttings by cyclone rotation, comprising the following steps: (1) Control of system viscosity: reducing viscosity of oil-based mud cuttings by heat exchange between a gas medium and the cuttings to reduce interaction force of oil and water with solid particle surfaces and pores, thereby facilitating separation in a cyclone field; (2) Cyclone rotation deoiling: among a coupled motion of rotation and revolution of oil-based mud cuttings particles in the cyclone field, using the rotation of the cuttings particles to promote centrifugal desorption of solid surface oil, capillary oil and pore oil, and using a periodically oscillating centrifugal force generated by the revolution to accomplish separation and enrichment of oil, gas and solid phases, thereby achieving removal of the oil phase from the pores of the cuttings; and (3) Gas-liquid separation and reuse: performing gas-liquid separation on the oil-containing mixture produced in step (2) to realize reuse of base oil, circulation of the gas media, and harmless treatment of the cuttings.

2. A The method of claim 1, wherein in step (1), the control of the system viscosity is carried out in the cyclone field, wherein a turbulent flow field in the cyclone field is utilized to promote heat exchange efficiency between the gas medium and the waste oil-based mud cuttings, so as to raise liquid temperature, thereby achieving the purpose of reducing the viscosity.

3. A The method of claim 1, wherein in step (1), the control of the viscosity is carried out at an operating temperature ranging from 70° C. to 200° C., depending on the formulation of the waste oil-based mud, and lower than the rated use temperature of the waste oil-based mud.

4. The method of claim 1, wherein in step (1), the gas medium includes air, nitrogen, supercritical carbon dioxide gas, hydrogen, dry gas, gas from a low pressure separator, and tail gas from natural gas combustion.

5. A The method of claim 1, wherein in step (2), the oil-based mud cuttings particles have the coupled motion of cyclone revolution and particle rotation in the cyclone field; the rotation has a speed of at most 5000 revolutions/second; and a residence time is 2-10 seconds.

6. A An apparatus for deoiling of oil-based mud cuttings by cyclone rotation, comprising: a gas feeding system (1) and a gas heating system (2) connected to the gas feeding system (1) for heating a gas medium; a cyclone separator set (3) connected to the gas heating system (2) for deoiling of waste oil-based mud cuttings by cyclone rotation; and a gas-liquid separation and reuse system (4) connected to the cyclone separator set (3) for separating, circulating and reusing an oil-containing mixture exiting an overflow port of the cyclone separator.

7. A The apparatus of claim 6, wherein the apparatus further comprises: a conveying system (5-1) connected to the gas heating system (2) for conveying the waste oil-based mud cuttings to be treated; a conveying system (5-2) connected to the cyclone separator set for conveying the waste oil-based mud cuttings which have been treated; and a cuttings tank (6) connected to the conveying system (5-2) for storing the waste oil-based mud cuttings which have been treated.

8. The apparatus of claim 6, wherein the cyclone separator set (3) is a combination of 1-10 cyclone separators in series, and can be connected in parallel in multiple stages depending on treatment load.

9. The apparatus of claim 6, wherein the cyclone separator set (3) is assembled by installing the cyclone separator(s) in a normal arrangement, installing the cyclone separator(s) in an inverted arrangement, or installing the cyclone separators in a combination of a normal arrangement and an inverted arrangement.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The accompanying drawings are provided for further understanding of the disclosure. They constitute a part of the specification only for further explanation of the disclosure without limiting the disclosure.

[0031] FIG. 1 shows a process flow of the method for deep deoiling of oil-based mud cuttings by cyclone rotation according to a preferred embodiment of the present invention.

[0032] FIG. 2 shows particle size distributions of the waste oil-based mud cuttings particles used in an embodiment of the present invention.

[0033] FIG. 3 shows mesopore distributions of the waste oil-based mud cuttings particles used in an embodiment of the present invention.

[0034] FIG. 4 shows surface area distributions of the waste oil-based mud cuttings particles used in an embodiment of the present invention.

[0035] FIG. 5 shows viscosity-temperature curves of the waste oil-based mud used in an embodiment of the present invention.

[0036] FIG. 6 shows the deep deoiling effect of an oil-based mud cyclone separator according to an embodiment of the present invention.

DETAILED DESCRIPTION

[0037] After extensive and intensive research, the inventors of the present application have reached the following findings: because shale is very dense with an extremely low porosity (from 2% to 4%) and an extremely poor permeability (from 0.0001 mD to 0.1 mD), it's difficult for the pore oil in the waste oil-based mud cuttings particles to leave the nano- to micro-scale pores; on the other hand, the waste oil-based mud cuttings particles have a rotation speed of up to 5000 revolutions per second in a cyclone field, whereby a centrifugal force greater than viscous resistance can be provided, so as to promote the removal of the pore oil; at the same time, the cyclone rotation process is short in time, and the temperature required for heating to reduce viscosity is also lower than that required by a traditional process, thereby effectively increasing the treatment efficiency and reducing the energy consumption.

[0038] Based on the above research and findings, the inventors have creatively developed a method and an apparatus for efficient deoiling of waste oil-based mud with a driving gas. The advantages include simple process, easy operation, high deoiling efficiency, low energy consumption, etc., and the problems in the existing technologies have been solved effectively. The oil content of the cuttings treated according to the present disclosure is as low as 0.16% or less, about half of the maximum allowable content (0.3%) of mineral oil in GB4284-84 “Control standards for pollutants in sludges from agricultural use”. The residence time of the cuttings in the cyclone separator set is less than 5 s, so the treatment time is much shorter than that of a conventional treatment method. Therefore, harmless treatment of oil-based mud cuttings with high efficiency and low consumption is achieved.

[0039] In one aspect according to the present disclosure, there is provided a method for deep deoiling of oil-based mud cuttings by cyclone rotation, comprising the following steps:

[0040] (1) Control of system viscosity: reducing viscosity of oil-based mud cuttings by heat exchange between a gas medium and the cuttings to reduce interaction force of oil and water with solid particle surfaces and pores, thereby facilitating separation in a cyclone separator set;

[0041] (2) Cyclone rotation deoiling: among a coupled motion of rotation and revolution of oil-based mud cutting particles in the cyclone separator set, using the high-speed rotation of the cutting particles to promote centrifugal desorption of solid surface oil, capillary oil and pore oil, and using a periodically oscillating centrifugal force generated by the revolution to accomplish separation and enrichment of oil, gas and solid phases, thereby achieving deep removal of the oil phase from the pores of the cuttings; and

[0042] (3) Gas-liquid separation and reuse: performing gas-liquid separation on the oil-containing mixture produced in step (2) to realize reuse of base oil, circulation of the gas media, and harmless treatment of the cuttings.

[0043] In the present disclosure, the control of the system viscosity in step (1) is carried out in the cyclone field, wherein a high-speed turbulent flow field in the cyclone field is utilized to promote heat exchange efficiency between the gas medium and the waste oil-based mud cuttings, so as to raise liquid temperature, thereby achieving the purpose of reducing the viscosity.

[0044] In this present disclosure, the operating temperature for the control of the system viscosity in step (1) needs to be appropriately selected according to different waste oil-based mud formulations. In principle, it should be lower than the rated use temperature of the waste oil-based mud, and the temperature generally ranges from 70° C. to 200° C. Within this range, the oil phase of the waste oil-based mud will not be cracked.

[0045] In the present disclosure, in the deoiling process with the aid of the high-speed rotation caused by the cyclone in step (2), the motion of the oil-based mud cuttings in the cyclone field is a coupled motion of cyclone revolution and particle rotation. The rotation speed is up to 5000 revolutions per second, and the residence time is 2 to 10 seconds.

[0046] In the present disclosure, the gas medium used for driving oil with cyclonic gas is air, nitrogen, (supercritical) carbon dioxide gas, hydrogen, dry gas, gas from a low pressure separator, tail gas from natural gas combustion, etc.

[0047] In a second aspect of the present disclosure, there is provided an apparatus for deep deoiling of oil-based mud cuttings by cyclone rotation, comprising: a gas feeding system, a gas heating system, a cyclone separator set, a gas-liquid separation and reuse system, a conveying system and a cuttings tank, wherein:

[0048] the gas feeding system and the gas heating system are used to heat the gas medium;

[0049] the cyclone separator set is used for deep deoiling of the waste oil-based mud cuttings under high-speed rotation caused by the cyclone;

[0050] the gas-liquid separation and reuse system is used to separate, circulate and reuse the oil-containing tail gas exiting the overflow port of the cyclone separator; and

[0051] the conveying system and the cuttings tank are used to convey and store the waste oil-based mud cuttings before and after the treatment.

[0052] In the present disclosure, the cyclone separator set is a combination of 1-10 cyclone separators in series, and can be connected in parallel in multiple stages depending on the treatment load.

[0053] In the present disclosure, the cyclone separator set is assembled by installing the cyclone separator(s) in a normal arrangement, installing the cyclone separator(s) in an inverted arrangement, or installing the cyclone separators in a combination of a normal arrangement and an inverted arrangement.

[0054] Reference will be now made to the accompanying drawings.

[0055] FIG. 1 shows a process flow of the method for deep deoiling of oil-based mud cuttings by cyclone rotation according to a preferred embodiment of the present invention. As shown by FIG. 1, a gas medium enters a gas heating system 2 from a gas feeding system 1. After the gas medium is heated, it is mixed with the waste oil-based mud cuttings input from a first conveying system 5-1, and the resulting mixture enters a cyclone separator set 3. The cyclone velocity field in the cyclone separator set 3 can increase the turbulence of the gas. The increased turbulence promotes convective heat transfer between the gas medium and the waste oil-based mud cuttings particles, and thus helps reduce the viscosity of the waste oil-based mud cuttings, thereby facilitating dispersion of the particles and removal of the oil phase. At the same time, the periodically oscillating centrifugal force generated by the revolution of the cuttings particles in the cyclone field is utilized to remove the free oil and part of the capillary oil, and the centrifugal force generated by the high-speed rotation is utilized to remove the capillary oil, surface oil and pore oil, so as to achieve deep deoiling of the waste oil-based mud cuttings. The waste oil-based mud cuttings particles that have been deeply deoiled are discharged from the bottom outflow port of the last stage of the cyclone separator set 3, and sent to a cuttings tank 6 by a second conveying system 5-2 for resource utilization, for example, paving a road at a well site, burning bricks, etc. The liquid phase (composed of oil, water, etc.) obtained by the deoiling enters a gas-liquid separation and reuse system 4 along with the gas medium. The gas medium returns to the gas feeding system 1 for circulation, and the liquid phase is transported by tanker to a mud station for reuse, thereby achieving harmless treatment of the waste oil-based mud cuttings and maximizing reuse of the resources.

EXAMPLES

[0056] The invention will be further illustrated with reference to the following specific Examples. It is nevertheless to be appreciated that these Examples are only intended to exemplify the invention without limiting the scope of the invention. The test methods in the following examples for which no specific conditions are indicated will be carried out generally under conventional conditions or under those conditions suggested by the manufacturers. Unless otherwise specified, all parts are parts by weight, and all percentages are percentages by weight.

Example 1

[0057] For oil-based mud drilling in a shale gas area, the waste oil-based mud was deoiled using the method and apparatus according to the present disclosure. The specific operation process and effects are described as follows:

[0058] 1. Measurement of the Physical and Chemical Properties of an Oil-Based Mud Cuttings Sample

[0059] 1) Measurement of the Contents of the Oil, Water and Solid Phases

[0060] A Soxhlet extractor and a CCl.sub.4 solvent were used to extract the waste oil-based mud cuttings. The oil content of the sample was 19.4% as measured by an infrared spectrophotometer. After drying, the solid content of the sample was 63.1%, and the water content was 17.5%.

[0061] 2) Measurement of the Particle Size of the Cuttings Particles

[0062] The particle size of the cuttings particles has a direct influence on the magnitude of the centrifugal force applied on the cuttings particles in the cyclone separator. The particle size distribution of the extracted cuttings particles measured by a laser particle size analyzer is shown by FIG. 2. The particle size distribution ranged from 0.15 μm to 976.48 μm; the average diameter was 202.73 μm; the median diameter was 163.49 μm; and the standard deviation was 226.63 μm.

[0063] 3) Measurement of Nitrogen Adsorption

[0064] The specific surface area and pore volume of the extracted oil-based drill cuttings particles were measured with an automatic nitrogen adsorption instrument. As shown by FIGS. 3-4, the average surface area of the particles was 9.43 m.sup.2/g; the average pore volume was 0.0372 cm.sup.3/g, and the average pore size was 163.47 μm. FIGS. 3-4 show that the oil-based drill cuttings particles were porous systems with irregular surface morphology. The cuttings pores were mainly in the mesoporous range, so deoiling was very difficult.

[0065] 4) Measurement of Viscosity-Temperature Curve

[0066] A rotor viscometer was used to determine the variation of the dynamic viscosity of the waste oil-based mud liquid sample during the heating process. As shown by FIG. 5, after the sample was heated to 128° C., the viscosity had little change when the heating continued. At this point, the dynamic viscosity of the sample had decreased from 17500 cP (centipoise) at the initial temperature to 226 cP, a decrease of about 80 times. The test results show that heating of the waste oil-based mud can effectively reduce its viscosity, and the selection of the temperature of the heating gas medium is guided.

[0067] 2. Implementation Process

[0068] In this Example, air was selected as the gas medium. The air was heated by an air duct electric heater. A screw conveyor was used for material transportation.

[0069] The air was pumped in by an air feeding system at 200 m.sup.3/h and heated to 160° C. by a gas heating system. Oil-based mud drill cuttings were transported by a conveying system at a feed rate of 50 kg/h. The gas and solid phases entered a cyclone separator set for deep deoiling treatment. The treated solid phase entered a cuttings tank, and the rest of the material entered a gas-liquid separation and reuse system. A sampling port was provided at the bottom outflow port of each stage of the cyclone separator set for sample analysis.

[0070] 3. Implementation Effects

[0071] 1) Deoiling Effect

[0072] Upon theoretical calculation, the calculated residence time of the cuttings particles in the cyclone separator was used as the cyclone rotation deoiling treatment time, and the calculation result was that the residence time of each stage was about 0.3 s. The Soxhlet extraction-infrared spectroscopy method was used to measure the oil content of the drill cutting particles from the bottom outflow port of the cyclone separator at each stage, and the deoiling efficiency of each stage relative to the starting material was calculated. As shown by FIG. 6, after treatment for 2.7 s, the oil content of the drill cuttings particles was 0.16%, far lower than the oil content of less than 0.3% required by GB 4284-84 “Control standards for pollutants in sludges from agricultural use”, and the deoiling efficiency reached 99.2%.

[0073] 2) Properties of the Recovered Mud

[0074] The recovered oil-based mud was sampled from the gas-liquid separation and reuse system, and its property parameters were measured as shown in Table 1. As known from the results, the recovered oil-based mud met the requirements for reformulation and reuse of oil-based mud.

TABLE-US-00001 TABLE 1 Property parameters of recovered oil-based mud Parameter/unit Measured Value Density/(g/cm.sup.3) 1.40-1.62 Funnel viscosity/s 50-90 API (American Petroleum Institute) ≤2 filtration (static filtration)/mL Basicity (Pom)/mL 1.2-2.5 Gel strength/Pa  4-6/10-12 Sand content/% ≤1 Plastic viscosity/MPa .Math. s 20-35 Yield point/Pa 10-25 Solid content/% 15-20 HTHP (high temperature and high pressure) ≤3 filtration (high temperature and high pressure filtration) MBT (bentonite content)/(g/L) 10-20 K.sub.f (friction coefficient)   <0.10 Emulsion-breaking voltage/V 762  Undissolved lime/(kg/m.sup.3) 2-9 CaCl.sub.2 content in aqueous phase/wt % 20-30 Oil/water ratio 70-80/20-30

[0075] 3) Estimation of Energy Consumed by the Apparatus

[0076] Based on the energy consumed in the test process, the energy consumed by an industrial apparatus with an annual treatment capacity of 84000 tons was estimated. The energy consumed by the main electrical devices is shown in Table 2 below:

TABLE-US-00002 TABLE 2 Energy consumed by the devices Annual Operating electricity Number of devices hours per consumption/×1000 No. Device Voltage/V Operating Spare Power/kW year/h kWh 1 Screw conveyor 380 1 — 4 8400 33.6 (feeding) 2 Screw conveyor 380 1 — 2 8400 16.8 (transporting) 3 Screw conveyor 380 1 — 1 8400 8.4 (discharging) 4 Air blower 380 1 1 200 8400 1680 5 Air duct electric 380 1 — 1000 8400 8400 heater Total 1207 10138.8

[0077] The total annual energy consumption is equivalent to 871.78 tons of standard oil, and the energy consumption of the treatment of waste oil-based mud cuttings is 10.38 kg/t standard oil.

[0078] In summary, the implementation of this technology can effectively reduce the running cost of the process, save resources, protect environment, and meet the strategic direction towards “low carbon, green, efficient, energy saving” sustainable development.

[0079] The Examples listed above are only preferred examples in the disclosure, and they are not intended to limit the scope of the disclosure. Equivalent variations and modifications according to the disclosure in the scope of the present application for invention all fall in the technical scope of the disclosure.

[0080] All of the documents mentioned in the disclosure are incorporated herein by reference, as if each of them were incorporated herein individually by reference. It is to be further understood that various changes or modifications to the disclosure can be made by those skilled in the art after reading the above teachings of the disclosure, and these equivalent variations fall in the scope defined by the accompanying claims of the application as well.