Patent Application
20130014950
The present invention relates to a method for cleaning a producing oil well with a thermal convertor; and specifically, to a thermal convertor for the generation of vapors, including steam, for use in various well-treatment applications in the oil and gas production including well stimulation and corrosion inhibition.
Oil producers have long known that existing wells clog over long periods of production and such clogging causes diminished flow to occur as normal well pressure declines with the production of oil. Solutions include chemical treatments, heating wells to temporarily reduce paraffins and high asphaltenic portions which may be clogging the well, and simple washing out the well bore to sweep away the offending particulates, These treatments clean the well bores or production tubing, modify the viscosity of oil, or prevent high molecular weight hydrocarbons from solidifying in a well bore thereby making the production of additional crude oil from such wells economically producible. Other uses of vapor streams described herein are similar to techniques well known to those in this industry but use novel methods and improved apparatus to achieve previously unachieved results. The usefulness of the present invention will be apparent after this disclosure. The present disclosures relates to an apparatus for delivery of superheated vapors, including saturated steam, if required, and treating chemicals for the purpose of well-stimulation and corrosion inhibition.
The present system can generate a useable stream of inert vapors using readily available fuels, such as—without limitation—diesel, propane or natural gas, for these uses. The system is small and light enough to permit trailering to the site of use by a regular towing hitch. The methods disclosed herein increase oil recovery from old existing wells without costly reworking of the wells or the expenditure of huge expenditures of money for energy to drive the system.
This method of cleaning a well bore including a rat hole below the perforations of the producing zone is accomplished by the operator removing all production equipment from the well; reinserting the open ended production tubing without the production equipment to a point below the perforations; circulating superheated vapor from a surface thermal convertor for at least thirty minutes through the annulus and returning up the production tubing until the returns are clean; step-wise lowering the production tubing into the well bore until the well bore including the rathole returns are clean; pressurizing the near well bore production formation by partially closing the wing valve on the return for a short or abbreviated period, typically about 15 seconds duration, then rapidly releasing the built-up pressure until the near well bore return is clean; and, incrementing the time of shut-in in similar abbreviated time increments, of again about 15 seconds, so that the second iteration would be approximately about 30 seconds, then 45 seconds, and repeatedly releasing pressure until the formation break-in pressure and permeable flow rate is established.
This well bore cleaning technology is preferably performed by pulling a production string and replacing the open or unattached tubing without the pump assembly to a position the greater of ten feet below the production perforation or three feet above resistance from well bore solids and build-up; injecting high-pressure superheated vapor in the annulus and allow a return up the production tubing for a period of at least thirty minutes; circulating superheated vapor to clean the well bore until the return is clean; incrementally adding subs to the production string to extend the string to the maximum depth and continuing the clean out of the well bore.
The injection of one or more selected vapors into a well bore to clean the well bore follows the similar steps of pulling all pumping rods and production equipment from the well bore; sweeping a wellbore by delivering the superheated gas and vapor-phase cleaning agents to the near and extended near wellbore formation; cleaning the wellbore by delivering the superheated gas for a short interval while inhibiting outflow from the wellbore, and rapidly relieving back pressure to induce movement of fines and sediment from the near and extended near well bore to a surface collection outlet; rinsing the well bore using saturated steam; dehydrating the well bore with the continued introduction of the superheated inert gas stream without additional water; connecting a thermal convertor comprised of a source of fuel providing a controlled flow of fuel, a source of compressed air providing a controlled flow of gas, a source of other liquids providing a controlled flow of such liquids to the thermal convertor, a mixer connected to both the source of fuel and the source of compressed air to combine the fuel and air flows in a homogeneous mixture, a water cooled combustion chamber with a controlled ignition source connected to the mixer to burn the homogeneous mixture of fuel and air at a specifically controlled temperature, and an outlet port from said combustion chamber providing a controlled outlet flow of near-oxygen free vapor, to a well bore; selecting one or more liquids to add to the controlled outlet flow of superheated vapor from the combustion chamber to vaporize said one or more liquids and injecting said selected combined vapor stream into a well bore for a period of time; and, disconnecting the thermal convertor and initiating production from the well after the period of time.
One liquid injected in its vapor phase is an alkali metal hydride and can additionally contain a non-ionic cleaning and wetting agent and selected environmentally safe or green terpenes or another naturally-occurring essential oils.
The thermal convertor additionally can provide a catalytic convertor at the outlet from the combustion chamber to provide all exhaust vapors are low in NOx gases. The flow through the outlet from the combustion chamber can regulated by a backpressure valve. The both permits the use of diesel as a fuel for the thermal convertor, making the use of the tool easily accomplished in remote locations and restricting the flow of superheated vapor into the well bore as the option of the operator. The thermal convertor of the present application can also and alternatively be operated on propane or methane gas or any other available and combustible gases.
A method of cleaning an oil well stimulates additional production by generating a superheated inert gas; sweeping a wellbore by delivering the superheated gas and one or more vapor-phase cleaning agents to the near and extended near wellbore formation; cleaning the wellbore by delivering the superheated gas for a short interval while inhibiting outflow from the wellbore, and rapidly relieving back pressure to induce movement of fines and sediment from the near and extended near well bore to a surface collection outlet; rinsing the well bore using saturated steam; dehydrating the well bore with the continued introduction of the superheated inert gas stream without additional water; and, continue pressurizing the formation to create a pressure drive to enable increased production of oil.
The cleaning of the wellbore of the present application also includes the rathole; that is, that extra hole drilled at the end of the well (beyond the last zone of interest) to ensure that the zone of interest can be fully evaluated. The rathole is typically below the perforations for producing wells and slowly fills with sand and corrosion products throughout the production from the well.
The treatment of well bore described foresees chemically treating the well through the introduction of an alkali metal hydride in a vapor phase in the amount of 0.00125% to 0.01% by weight into the well bore and extended well bore to treat formation surfaces to break up and clean out the production zone to increase the flow of oil from the formation and inhibit the production of carbonic acid from the carbon dioxide in the well bore minimizing acid corrosion of the well bore tubulars.
The application of a corrosion treatment to a well follows a similar process wherein the well is treated by generating a superheated inert gas; sweeping a wellbore by delivering the superheated gas and vapor-phase cleaning agents to the wellbore and production tubing; cleaning the wellbore and rathole by delivering the superheated gas for a short interval, and rapidly relieving back pressure to induce movement of fines and sediment from the well bore and rathole; rinsing the wellbore and production tubing with saturated steam to remove all chemical cleaning agents; drying the wellbore and production tubing with superheated inert gas; vapor phasing a solution of alkali metal hydride, such as sodium metasilicate from about 5 to 10% by volume and injecting down the annulus and up through the production tubing to coat the surfaces; and continuing injection of superheated inert gas to cure and set the alkali metal hydride in the well bore and production tubing for corrosion inhibition.
All of the treatment methods described herein are accomplished using a thermal convertor which is fashioned utilizing a source of fuel providing a controlled flow of fuel; a source of compressed air providing a controlled flow of air; a source of water providing a controlled flow of water; a mixer connected to both the source of fuel and the source of compressed air to combine the fuel and air flows into a homogeneous mixture; a water cooled combustion chamber with a controlled ignition source connected to the mixer to burn the homogeneous mixture of fuel and air at a specifically controlled temperature; and, an outlet port from said combustion chamber providing a controlled outlet flow of vapor.
The thermal convertor can further provide a source of chemicals connected to the outlet port from the combustion chamber to provide chemicals to the vapor stream produced by the combustion chamber. The outlet port from the combustion chamber can be directed to a catalytic convertor, which not only cleans the combustion products from the convertor but also raises and maintains the temperature of the outlet vapors.
A back-pressure valve can also be positioned on the outlet port to control the flow throughput of the combustion chamber allowing both the use of diesel as a fuel and precise control of the amount of superheated vapor flowing into the well bore.
The preferred chemical treatment of a cleaned well bore can further be accomplished by spotting the production tubing between six to eight feet below the lowest perforation of the production zone to permit a pump mechanism to occupy a space within the static fluid level of the well bore; injecting vapor phase well treatment chemicals into the well bore and into the producing zone; and, starting the prime mover to move oil up the production tubing to the surface.
Re-treatment of the previously cleaned well bore with additional chemicals is readily accomplished by stopping the prime mover in the producing well bore and allowing the pump mechanism to be covered in the static fluid level; attaching the thermal convertor and injecting well treatment chemicals in vapor phase into the well bore production zone at a pressure above the break-in pressure of the formation for the producing zone, and continuing to inject superheated gas and vaporized well treatment chemicals. After this treatment, further production can proceed as long as a gas-liquid seal is maintained in the near-well bore production zone. A gas-liquid seal is defined as the coverage of formation liquids, which may include both oil and water, over the perforations in the producing zone. The well treatment chemicals are a non-ionic surfactant and a solvent, wherein the non-ionic surfactant is no more than 20% and the solvent, such as a environmentally safe terpene or other essential oils, is at least 80% of the well treatment chemicals by weight.
Irrespective of the source of the fuel, an electronically controlled shut down valve (not shown) can be activated to stop the flow of fuel from supply line 11 automatically because the fuel supply line is monitored for abnormal pressure or temperature before reaching another electronically controlled valve that can be throttled to open or close the fuel supply line 11 before reaching the combustion chamber 60. A check valve (not shown) prevents backpressure migration of the combustible fuel or hot vapor into the supply line 11.
The compressed air source 20 feeds in parallel with the fuel source line 11 to the combustion chamber 60. Built-in safeguards control the flow of compressed air into the combustion chamber. Shutdown valves (not shown) are electronically controlled by sensors (not shown) that signal the fuel line to immediately stop the flow of air through air supply line 21 to the combustion chamber 60 if required to prevent further burning. The compressed air line 21 can also provide a flow control valve arrangement (not shown) to vary as required the amount of gas reaching the gas/gas (not shown) mixer when utilizing alternative gaseous fuel mixes, immediately before the mixed air and fuel is introduced into the combustion chamber 60.
The water 30 supplied to the outlet side of the thermal convertor assembly 100 from source 30 receives a pressure boost from water pump driven by an electronically controlled motor, which can be activated if steam is desired to be used in the well bore. Since water cannot be used in some types of formations, steam may not be useful in all situations, especially in formations have water reactive clays and the like. This water source 30 can also provide coolant for the combustion chamber 60. A check valve can be provided to assure that water does not flow back into the water supply 30. The combustion chamber 60 is water cooled in a closed loop system similar to an automobile cooling system. Alternatively, the water could flow from source 30 through the line to the combustion chamber jacket (not shown in this view), then through a radiator or heat exchanger before being returned to the combustion-chamber water jacket for recirculation around the combustion chamber, all in a manner well known to those in this art. The outlet side of the combustion chamber 71 can additionally be supplied with a catalytic convertor 63, which both removes unwanted NOx pollutants and increases the heat of the output vapor stream 70 of the system.
In
Operating temperatures range from 200° F. to 800° F. under normal conditions, but the system can be increased to generate 1200° F., if required. If the combustion chamber 60 reaches or exceeds a predetermined set point, e.g., 650° F. (343° C.), air, fuel, chemical injection (if any) and water are all automatically shut off and a back-pressure valve 65 is fully opened. If flame out occurs in the combustion chamber 60 as determined by having the temperature fall below 250° F. (121° C.), or excessive pressure is sensed as indicated by a pressure sensor (not shown) experiencing a exhaust pressure above a set point of 390 psi (2.69 MPa), a similar shut down sequence is activated.
The exhaust side 69 of the combustion chamber 60 is directed to the well head flow line (not shown) to supply the superheated combustion gases to the well bore; and will be conducted to the well head by means well known to the oil field trade and process industries. The outlet side 69 of the combustion chamber 60 is monitored for pressure, temperature and rate of flow. If the pressure exceeds acceptable safety limits, it can be vented to the atmosphere through a safety valve (not shown, but well known in this art).
By careful regulation of the combustion, the amount of remaining oxygen in the outlet flow 70 of superheated gas is reduced to 0.1% to 0.3% oxygen, far less than the 3% to 5% oxygen found in most membrane injection systems. Programmable logic devices constantly monitor the O2 levels in the system 100 of
Similarly, a control valve 65 can be preset at 390 psi (2.69 MPa) to relieve pressure on the system automatically. An electronically controlled back pressure control valve can provide further control over the system by opening or closing the outlet of the combustion chamber 60 thereby regulating the flow of vapors from the chamber 60. This valve 65 also permits the use of diesel fuel by supporting the auto-ignition sequence in the combustion chamber 60 from the glow plug 15 by substantially closing outlet 69 from the combustion increasing pressure in the combustion chamber 60.
A chemical supply valve (not shown) is opened allow the flow of chemicals from source 40 (as shown in
The accumulated pressure can then be dumped at the surface (not shown) and the process repeated until the return fines and lifted solids are clear. It is best to never completely close the wing-valve 340 to prevent the lifted fines and solids from resettling into the well bore WB and rathole 360 during these successive phases of activity. Subs can be added to the production tubing as shown in
As shown in
It would not be unusual as this point is reached to start finding fracing particles returned upon the pressure release at the wing-valve on the surface (not shown in this view). This suggests the well has been cleaned to the production zone of all solidified particulate matter and is ready to flow.
The circulation of superheated inert gas in this manner cleans the wellbore WB, near-wellbore 510 and extended well bore 520 of paraffins, asphaltenes and other forms of accumulated sediment which may have clogged the well bore perforations 650 and restricted permeability of the formation.
As shown in
The chemical treatment of the production formation is begun by injecting the superheated vapor into the newly cleaned well bore WB and near well bore 510 to reduce the interfacial surface tension of the production zone rock and to modify the wettability of the near 510 and extended wellbore 520. This cleaning process is done using a bio-degradeable cleaning/wetting agent, as well as other agents such as terpenes and other naturally occurring essential oils. This treatment customarily requires a fifty-five gallon drum for a twenty-foot production zone. Larger production zones may require additional drums of cleaning/wetting agent. Other non-bio-degradeable solvents could be substituted for this cleaning step. Then, steam can be injected into the well bore WB to rinse the wetting/cleaning agent from well bore WB. The steam is then terminated and the superheated inert gas is continued without the steam or chemical to dry or dehydrate the formation and prepare it for an alkali metal hydride solution similar to sodium meta-silicate, and an available product called FlowMorAH™ available from Fontus Chemicals of Houston, Tex. This treatment process also allows, in receptive geological formations, the accumulation of attic gas, which provides additional driving forces on the oil well. For example, in
This treatment provides a film coating on the surface of the geologic formation and provides a hydrocarbon-phobic surface that resists oil rewetting or accumulation of the production zone. The superheated gas treatment is continued until the inert gas accumulating in the well bore WB creates sufficient pressure or attic gas 710 to sustain production of oil into the wellbore WB for removal in a manner well-known in the art using the standard artificial lift mechanism.
Re-treatment of the well is easily accomplished by returning to the well which has shown decline in the achieved production rate from the initial treatment. The superheated gas is again injected into the well bore WB with associated chemical treatment using a non-ionic surfactant aqueous wetting agent, such as FloMorAQ™ also available from Fontus Chemicals of Houston, Tex.
Well treatment, in highly corrosive wells, using the thermal convertor can be readily accomplished by cleaning the well using the process described herein for the clean-out process until the fines are removed. Using the same technique previously described, a silicon based metal hydride is vapor deposited on the annulus and production tubing by running at least a fifty-five (55) gallon drum of the material through the clean well bore string, containing no more than twenty percent (20%) by volume of the alkali metal hydride.
The fresh alkali metal hydride is then cured in the well annulus and production tubing by continuing the flow of superheated vapor from the thermal connector without steam to cure the product thereby forming a corrosion resistant surface on the annulus and production tubing.
The use of the superheated vapor delivery system of the present application can be used for limited periods of time to lift oil from the production zone to the surface by building pressure in the annulus and opening and closing the wing-valve at the production tubing repetitively. The adjustment of the pressure caused by the opening and closing of the wing-valve lifts the product to the wellhead.
The particular embodiments and uses disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the invention. Accordingly, the protection sought herein is as set forth in the claims below.
