Light weight drilling fluids are provided while drilling a well, by introducing bubbles to the fluid. Utilizing primary compressors and a booster compressor, the system responds to interruptions and resumptions of air supply during drill pipe connections and other abrupt or significant changes in system demand, by allocating air (or other gas) into the drilling fluid or into a compressed gas storage and/or recycling system. The system is versatile in that it may deliver 100% air (gas) to the drill pipe, and may be used in contexts other than well drilling.
In drilling wells for oil and gas, air drilling has been used successfully for many underbalanced and other drilling operations, but, as is the case with many other technical processes, air drilling could benefit from improvements. A particular problem with air drilling is the resumption of desired downhole pressure and flow when drilling is interrupted to make piping connections. As the drill continuously penetrates into the earth, additional sections of pipe must be secured to the existing piping, creating a transition interval (“connection time”), which necessitates highly reduced pressures and reduced downhole flow, if any. Almost always, the air compressors are kept operating in one mode or another in order to be able to respond immediately to a renewed call for air flow, wasting energy and sometimes causing overheating and damage to the compressors. Inadequate circulation of drilling fluid around the drill bit for too long of an interval can also result in a stuck drill bit, among other difficulties well known in the art. The industry has developed various techniques to ameliorate these problems, but they continue to plague the operators. A basic requirement of an air supply system for air drilling is the ability to deliver a steady and reliable flow of air at the desired pressure. But, even apart from the problem of connection time, the demand for air is not always steady. Another problem more or less endemic in air drilling is the occasional sudden shift in demand for air as the drill bit penetrates through strata presenting different pressures, even greatly reduced pressures such as may be presented by penetrating an unforeseen cavity in the earth formation. Sudden demands for significantly higher pressures mean sudden demands for significantly higher air volume, since air is compressible. An inability to deliver the appropriate amount and pressure of air in a short interval can result in unwanted intrusions of fluid and other matter into the wellbore, or unnecessary losses of fluid into the formation strata.
Contemporary air drilling rigs commonly utilize rotary centrifugal air compressors—usually two or more—coupled to a positive displacement, usually reciprocating piston, booster. This arrangement has a history of providing a reliable supply of air during steady state conditions, but tends to be inefficient in that it produces more compressed air than is actually used downhole, and it is difficult to control in periods of rapidly changing demand. In many situations of changing demand, the compressors and booster either tend to “fight” each other, or far too much air is simply vented, resulting in significant wastage of energy. In some cases, either the booster or a compressor will become overloaded and break down due to overheating, causing much expense and delay to the operator.
Foams have been used frequently where light weight drilling fluids are desired. Generally, foams have a very high percentage of air or other gas and a density less than three pounds per gallon of fluid. Frequently the operators will monitor drilling fluid density and/or hydrostatic head, and try to control them for various reasons. For some applications, such as many underbalanced drilling operations, it would be desirable to use drilling fluids in the range of 5 to 8 pounds per gallon, but the art has been slow to develop such fluids. For many drilling operations, an ideal system would provide drilling fluids of various weights in rapid response to the conditions encountered or the changing specifications of the operators for whatever reason.
Our system provides practical solutions to the above described problems and desiderata. We are able to deliver a steady supply of air or other gas to the well head for introduction to the well during drilling while also being able economically and efficiently to respond to sudden changes in demand for volume, pressure, and density. Our invention is able to significantly reduce the energy requirements of the compressors and boosters and at the same time respond quickly to abrupt changes in demand for air or other gas. Our compressed gas supply system can be used in any application requiring rapid, economical, responses to abrupt changes in demand.
Our invention is a method of regulating the delivery of compressed gas from a source of compressed gas to an end use line, the source comprising at least one primary compressor and a booster compressor for providing gas at a pressure above a predetermined value A, the booster compressor having a gas inlet and a gas outlet, the method comprising: (a) passing compressed gas into a volume bottle from the at least one primary compressor and regulating the quantity of gas within the volume bottle within desired limits; (b) while the use requirements for gas in the end use line include a pressure below the predetermined value A, passing gas from the volume bottle to the end use line; (c) while the use requirements for gas in the end use line include a pressure above the predetermined value A, (i) passing gas from the volume bottle to the inlet of the booster compressor and (ii) passing gas from the outlet of the booster compressor to the end use line; (d) when the use requirements for gas in the end use line include a pressure reduced suddenly from the pressure above the predetermined value A, recycling gas from the outlet to the inlet of the booster compressor, (e) when the use requirements for gas in the end use line include an end use pressure greater than the suddenly reduced pressure of step (d), ceasing the recycling of gas from the outlet to the inlet of the booster compressor, and (f) performing either step (b) or step (c).
Our invention is also a method of controlling and conserving compressed gas for use as a drilling fluid or component thereof, the compressed gas provided by at least one primary compressor and a substantially continuously operating booster compressor having gas intake means and gas output means comprising (a) providing a flow of gas from the output means of the booster compressor at an enhanced pressure of at least 400 psi to a drilling fluid line for use as a drilling fluid or component thereof, (b) when the pressure specification for drilling fluid in the drilling fluid line declines to a value substantially below the enhanced pressure, substantially reducing or terminating the flow of gas to the drilling fluid line and opening the flow of gas from the booster compressor to (i) a volume bottle and (ii) the intake means of the booster compressor, and (c) directing gas from the output side of the booster compressor to the intake side of the booster compressor, thereby conserving compressed gas by enabling the booster compressor to operate at a substantially reduced work level.
Also, our invention includes a method of making a light weight drilling fluid comprising compressing a gas with at least one primary compressor, further compressing the gas with a booster compressor, passing the gas at least partly from the booster compressor into a microbubble machine, passing a base drilling fluid into the microbubble machine, thereby making a dispersion of microbubbles in the base drilling fluid, and withdrawing a light weight drilling fluid from the microbubble machine.
In addition, our invention includes readily transportable apparatus for conserving compressed gas at a well drilling site, the well drilling site having at least one primary gas compressor and a booster compressor, and a line for conveying drilling fluid to a wellbore, the readily transportable apparatus comprising at least one gas line including means for connecting the compressors to the drilling fluid line, and a volume bottle in the line for buffering pressure changes in the gas line.
As indicated above, certain components used in our system are commonly found in the oil field. Certainly where air drilling is practiced, air or other gas compressors will be present, and accordingly our invention is adapted to utilize compressors and drilling rigs already on site. Accordingly, in one aspect, our invention, can be mounted on a skid or truck for transportation to a drilling site, where it can be connected to the compressors and drilling pipe. However, the advantages and uses of our invention are not limited to oil field applications—such a mobile system can be used in many other situations where compressed air is required; also the compressors can be equipped by the manufacturers or suppliers with the controls and valves necessary to carry out the invention.
Our invention may use gases other than air. Wherever we mention air, we could use, and we intend to include, nitrogen (see Chitty U.S. Pat. No. 6,494,262 for example), exhaust gas (Moody U.S. Pat. No. 5,663,121) or air from which a substantial part of the oxygen has been removed, resulting in a gas comprising more than 85% nitrogen, or any other practically available gas. Air, however, remains the most inexpensive and available gas. See King et al U.S. Pat. No. 5,249,635. Air is by far the most common gas utilized by a compressed air system comprising at least one primary compressor and a booster compressor. As used herein, a primary compressor is a compressor whose intake is from a low-pressure source, as the atmosphere, and a booster compressor is one whose intake is from an already somewhat pressurized source; this pressure will be increased by the booster compressor. Commonly, the primary compressor(s) are dynamic compressor(s) and the booster compressor is a reciprocating positive displacement compressor; however, we do not intend to be limited to these types of compressors. We do not intend to rule out the use of one or more compressors intermediate the primary and booster compressors, perhaps connected in series, but normally when two or three primary compressors are used, the second and third ones are employed as illustrated herein in order to assure the availability of larger volumes of air.
Our drilling fluid may be 100% air, but we also contemplate a drilling mud containing gas injected by our system. The gas may be introduced to the liquid drilling mud base in the form of substantially evenly dispersed microbubbles of one of the above named gases, thus creating a highly textured drilling fluid having substantially reliable properties.
As used herein, the term “microbubble” means a bubble having a diameter when first formed, regardless of the pressure at formation, from 100 nanometers to 100 micrometers, preferably from 20-40 microns in diameter. Depending on the drilling mud composition, at some concentration of gas, and certainly if more than 70% of the volume of the drilling fluid comprises air, the microbubbles may merge with each other and/or tend to form contiguous air pockets, forming the physical structure of a foam. Where the drilling fluid contains microbubbles, the bubbles will be compressed in high pressure zones, reducing their diameters, and some of the air or other gas may become dissolved in the fluid, which may alter the density of the fluid.
As used herein, the term “textured” means that the composition of the drilling fluid is substantially uniform, and particularly that the microbubbles remain in discrete, dispersed form although they may be more or less compressed depending on the pressure on the fluid. When we speak of the formation of microbubbles, we mean that the bubbles are of a size described above and are substantially evenly dispersed.
In
a, 4b, and 4c describe a cavitation device which can be used as a microbubble machine.
Referring now to
At least one of the compressors 1a, 1b, and 1c operates continuously, and is assisted by a booster compressor 8, here illustrated as a positive displacement compressor, in particular a reciprocating compressor. Air from the volume bottle 2 feeds through ball valve 20 to the low pressure inlet 17 on booster 8. The air is compressed in booster 8 and sent as high pressure air through outlet 30 and ball valve 28 to high pressure line 31. Depending on downstream (end use) air demand, control valve 29 may direct air from line 31 to volume bottle 2 Any positive displacement compressor, desirably a reciprocating compressor, may act as the booster (reciprocating compressor) 8 in our invention; double-acting and other configurations of reciprocating compressors may be used. The term “reciprocating compressor” as used herein is meant to include any functionally equivalent positive displacement compressor. The reciprocating compressor is used in our invention as a booster to increase the volume, pressure or flow of air available to the end use served by either high pressure end use line 31 or low pressure end use line 10. Persons skilled in the art will recognize that control valve 29 marks a boundary, indicated by a dotted line, between high and low pressure requirements for the equipment. We do not intend to be limited to reciprocating compressors and the type of booster illustrated in our invention; we may us any booster compressor as defined above.
As booster 8 is able to deliver substantially higher volume, pressure or flow than one or more compressor(s) 1a, 1b, and/or 1c acting without a booster, the valves, meters and the like, as well as the lines, such as line 31, themselves handling compressed air originating with reciprocating booster 8, are desirably engineered to handle high flows and pressures—for example from 500 to 5000 psi—while the low pressure portions such as manifold 26, line 10, and their associated valves, meters and related equipment, will normally handle pressures of 500 psi or below. Persons skilled in the art will realize that these values are merely examples, and other, different values (such as a predetermined value A, or alternatively 400 psi) or ranges may be designed into the system depending on the desires and objectives of the operators and the specifications of the compressors and other equipment, the point being that the booster is able substantially to increase the delivery of compressed air to the end use, while some applications or periods of operation may not require such high pressures and large volumes.
Automatic controls not shown are designed to utilize the recycling abilities (control valve 29 to low pressure inlet 17, for example) built into the system of
When full demand for air is resumed, the system is able to react immediately. Sensors, transducers, and flow meters in communication with controllers will open appropriate valves and activate the compressor capacity controls to permit the flow of air to the end use. Either high or low pressure can be supplied over a wide range of volumes and flow rates.
The system can move into a “ready” mode during an interruption of demand. The system recognizes that the booster 8 will be kept running at a low-demand pace determined normally by its internal controls or settings by the operator, but will automatically economize on fuel and compressed air by setting up a loop whereby compressed air passes from outlet 30 through valve 28 and line 31 to control valve 29, sending air to volume bottle 2; from volume bottle 2 air is returned to reciprocating compressor 8 through valve 20 and inlet 17. Relief valve 12 and automatic vent 14 provide safety against overload of volume bottle 2. Pressure, flow and volume controls not shown will draw on both the volume bottle 2 and the booster 8 as well as manifold 26 to resume quickly the supply of air in either of the end use lines 10 or 31. The system of
Low pressure air passes from line 10 (see low pressure end use line 10 in
A base drilling mud for use in well drilling is prepared or stored in a vessel not shown and sent by a charge pump not shown through flow meter 83, where a signal representing flow rate is generated and forwarded to the control system not shown. From flow meter 83 the base drilling mud is sent to low pressure microbubble machine 5, detailed in
Low pressure microbubble machine 5 receives drilling mud from line 21 and air from line 51, forming discrete and dispersed microbubbles of air in the drilling mud as explained with reference to
High pressure air may alternatively be delivered from a source in line 31 (see high pressure end use line 31 in
High pressure microbubble machine 13 comprises a housing forming a chamber holding a membrane tube as illustrated in
Gas or air at either high or low pressure from the system of
Thus, four options are shown in
The equipment should be engineered to handle the high pressures and flow rates frequently demanded in drilling practice. While a triplex pump is suitable and commonly used for high pressures and volumes, any pump able to provide the drilling fluid necessary for drilling may suffice. Persons skilled in the art may realize also that under some of the higher pressures common in the art, the microbubbles will be compressed or even dissolved in the liquid, and the density measurements should be adjusted accordingly. Normally, however, it is desirable for the microbubbles to be substantially evenly dispersed and have a substantially uniform size, preferably from 20 to 40 microns in diameter or generally from 100 nanometers to 100 micrometers in diameter, giving the modified fluid an even texture.
Proceeding now to
Except for primary compressors 1a, 1b, and 1c, booster 8, and the liquid drilling mud sources not shown, which are normally already on the drilling site, the equipment of
Operation of the system is as follows. A drilling rig is conducting a drilling operation in a well containing drill pipe downstream of Modules 3 and 4. The operators utilize a base drilling fluid which is mixed in or stored in a vessel or vessels not shown. On demand from the control system, the base drilling fluid is delivered, through one or both of flow meters 25 and 83, to microbubble machines 5 and/or 13, which are able to disperse finely divided microbubbles into the fluid in an amount and at a rate, proportioned to the flow rate of the base drilling fluid, to modify the density of the base drilling fluid and create a textured reduced-density drilling fluid for use in the well. Pressurized air for making the microbubbles is supplied from Module 1 in the manner described with respect to
As is known in the art of well drilling with air or liquid drilling fluid, a more or less steady flow of drilling fluid (or pressurized gas in the “air only” mode) is normally needed while the string of drill pipe moves downwardly, until another section of pipe is required. At this point, the flow of drilling fluid is temporarily halted or substantially reduced, either by control valves 27 and/or 38 or otherwise, and full pressure and flow will not be resumed until the connection of a new pipe segment is complete, lengthening the drill pipe string. In the past, such interruptions or disruptions in the substantially steady state of the system have caused difficulties for the operators because the dynamic compressors 1a, 1b, and 1c and related equipment such as booster 8 cannot practically be shut down. Much fuel and energy has been wasted by simply venting excess compressed gas (air) during the “down” connection time. In addition to interruptions in flow known as connection time, a more or less steady state demand can be disrupted by sudden changes in the formation pressure. Our system is able to provide the required air almost immediately on resumption of demand.
Referring further to
a and 4b are adapted from
Definition: We use the term “cavitation device,” or “SPR,” to mean and include any device which will cause bubbles or pockets of partial vacuum to form within the liquid it processes. The bubbles or pockets of partial vacuum have also been described as areas within the liquid which have reached the vapor pressure of the liquid. The bubbles or pockets of partial vacuum are typically created by flowing the liquid through narrow passages which present side depressions, cavities, pockets, apertures, or dead-end holes to the flowing liquid; hence the term “cavitation effect” is frequently applied. Cavitation devices can be used to heat fluids, but in our invention we use them to make microbubbles which are intended not to implode, but to remain in bubble form for incorporation into the base drilling fluid. To do this, a gas such as air is injected along with the base drilling fluid (liquid), and the conditions are controlled to generate microbubbles, preferably at a rate in response to the system's demand for density and flow. Cavitation devices of the type suggested herein can cause the bubbles to be dispersed and divided into quite small bubbles of substantially constant size.
The term “cavitation device” includes not only all the devices described in the above itemized U.S. Pat. Nos. 5,385,298, 5,957,122, 6,627,784 and 5,188,090 but also any of the devices described by Sajewski in U.S. Pat. Nos. 5,183,513, 5,184,576, and 5,239,948, Wyszomirski in U.S. Pat. No. 3,198,191, Selivanov in U.S. Pat. No. 6,016,798, Thoma in U.S. Pat. Nos. 7,089,886, 6,976,486, 6,959,669, 6,910,448, and 6,823,820, Crosta et al in U.S. Pat. No. 6,595,759, Giebeler et al in U.S. Pat. Nos. 5,931,153 and 6,164,274, Huffman in U.S. Pat. No. 5,419,306, Archibald et al in U.S. Pat. No. 6,596,178 and other similar devices which employ a shearing effect between two close surfaces, at least one of which is moving, such as a rotor, at least one of which has cavities of various designs in its surface as explained above, and which is capable of mixing a base drilling fluid and a gas to form substantially evenly dispersed and sized microbubbles.
a and 4b show two slightly different variations, and views, of a cavitation device suitable for the generation of microbubbles in our invention.
A housing 40 in
Another variation which can lend versatility to the SPR is to design the opposing surfaces of housing 40 and rotor 41 to be somewhat conical, and to provide a means for adjusting the position of the rotor within the housing so as to increase or decrease the width of the clearance 42. This can allow for different sizes of solids present in the fluid, to reduce the shearing effect if desired (by increasing the width of clearance 42), to vary the velocity of the rotor as a function of the fluid's viscosity, or for any other reason.
Operation of the SPR (cavitation device) is as follows. A shearing stress is created in the solution as it passes into the narrow clearance 42 between the rotor 41 and the housing 30. The solution quickly encounters the cavities 47 in the rotor 41, and tends to fill the cavities, but the centrifugal force of the rotation tends to throw the liquid back out of the cavity. Small bubbles, some of them microscopic, are formed. Where no gas is present, the small bubbles are imploded. The relatively large amount of gas present in the liquid in our invention, however, preserves the bubbles as microbubbles. The shearing, centrifugal force, and extreme turbulence effect excellent mixing. The texture of the drilling fluid can be observed in the substantial uniformity of bubble size and dispersion achieved by the cavitation device.
c is adapted from
It will be appreciated that the microbubble machine 13 can be constructed in various ways. For example, each membrane tube could be in a separate housing; a much larger number of membrane tubes than shown could be contained in a housing, more than one entrance for air or drilling fluid could be constructed, and the header and collector could be designed differently. We do not intend to be restricted to the particular design shown. Tubes can be constructed with the membrane on the internal surface, and the gas can be passed through the tubes to be injected into the liquid on the exterior of the tubes; indeed, for this mode, a tubular shape may not be of interest; dead-end bulbs having interior membrane surfaces, for example, would be operable.
Operation of the microbubble machine 13, as indicated above, requires that the air pressure between the membrane tubes 92 be higher than the fluid pressure within their interiors. Pressure within the membrane tubes will be affected by the original pressure in line 80, but also by flow rates within the membrane tubes, which in turn may be affected by the decreasing density or increasing volume of the fluid as it passes through the tubes, picking up microbubbles. Another factor will be the size of the membrane pores; smaller pores require greater gas pressure to assure the gas passes through the membrane tube walls, although this effect may be ameliorated by a larger number of pores. Generally, the transmembrane pressure difference should be at least 50 psi; for most uses, a transmembrane pressure difference of 75-200 psi may be used. The manufacturer may recommend a transmembrane pressure difference range.
This application claims the full benefit of Provisional Application 61/004,661 filed Nov. 29, 2007 and Provisional Application 61/062,932 filed Jan. 30, 2008, both of which are specifically incorporated herein in their entireties.
Number | Date | Country | |
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61004661 | Nov 2007 | US | |
61062932 | Jan 2008 | US |