Patent Application
20110180107
The present invention relates to drilling mud/particle separator screens or so-called “shaker screens” used during drilling boreholes for petroleum exploitation. More specifically, the invention relates to a method and a device for cleansing a shaker screen used in a drilling mud/particle separator, inspecting the shaker screen, identifying and registering significant wear on the shaker screen and repairing the shaker screen if significant wear is present, and returning the shaker screen for further use in borehole drilling.
Drilling of petroleum wells is conducted in that the drilling string is hollow and transports drilling liquid down to or in to a drill bit with nozzles. The drilling fluid returns with drilled out formation rock mass in the form of cuttings, rock particles, sand and metal particles back to the surface. The drilling liquid has high density and may be tixotropic or not, in order to bring along particles and cuttings back via the annulus and out of the borehole. The drilling liquid as such is an expensive liquid, it shall to a smallest, degree possible be released, and shall to a largest degree possible be recuperated. On the surface the drilling liquid and the cuttings via the primary separator plant normally comprising vibrating or rotating screen cloths.
Vibrating screen cloths (1) are used in so-called “shakers” for catching and vibrating out laterally that portion of the returning drilling mud or drilling liquid which is constituted by cuttings, sand and metal particles, and letting the drilling mud as such pass filtered through the screen cloth. The drilling mud is led over a series of one or more screen cloths (1), the coarser first, which removes the coarser particles, and later over finer and still finer screen cloths (1). Examples of such screen cloths arranged in frames are shown in
The entire screen assembly is vibrated in order to make drill cuttings and particles of all sizes to migrate out across the edge of the shaker screen frame so as for the drilling liquids liquid fraction and finer particles, below the shaker screen's mesh size will pass through the screen cloth. There are also screen cloths (1) arranged as an endless band which are arranged for rotating slowly. A shaker screen may comprise a rectangular main frame (2) of about 1×1 m2 and an example is shown in that the main frame may have 10 rows each of 20 rectangular oblong cell frames (22) each supporting its portion of a screen cloth.
Most shaker screen frames (2) comprise an upper screen cloth (1) with the desired mesh size, e.g. from 2500 gm (2.5 mm) for the very coarse screen, and down to 20 μm (0.020 mm), all with a backing of a support cloth with mesh size of between 2500 μm (2.5 mm) or 2000 μm (2.0 mm) or even 1000 μm (1.0 mm) which are all rather rough and durable. The screen cloth (1) and the support cloth (11) may be fixed to the cell frames (22) by means of adhesives or hardening cement mass so as for the screen cloth and the support cloth not to mutually vibrate and grind and thus to prevent that the screen cloth from be worn over the cell frame, and further prevent that the support cloth from being worn against the cell frame.
The so-called “cut point” of the screen cloth is defined by the size of the particles which have a given probability for being removed in a filter. Usually cut points may be indicated such as “D50 500” and “D90 500” defining 50% og 90% probabilities of being removed for particles of a given size, here 500 μm. For particles larger than the indicated “cut point” the probability for the particle to be sorted out is larger. For particles os a size less thann the indicated “cut point” the probability is larger to pass through with the mud.
A screen cloth initially has a given “cut point” which indicates the mesh size distribution of the apertures of the screen cloth, and indirectly indicates which size of particle sized which may pass through the apertures of the given mesh size distribution. The particle size distribution (PSD) affects the drilling liquid's properties and has an influence for example with regard to how far one may drill with the different borehole diameters, related to, among other factors, liquid pressure and resistance forces on the drill string such as torque. An article in the publication of the Society of Petroleum Exploration, SPE103934 “Successful Drilling of Oil and Gas Wells by Optimal Drilling Fluid Solids Control—A Practical and Theoretical Evaluation”, by B. Dahl, A. Saasen and T. H. Omland, describes disadvantages of wear of screen cloths.
A significant problem is that the screen cloth, which shall only let through a desired particle size, is worn and holes formed, and thus the screen cloth lets through particles as coarse as will be let through the support cloth, which in this example may be a standard mesh of 1000 μm. Thus the returning drilling liquid the desired particle size distribution and the desired maximum particle size for the further drilling operation. This is a known problem and the drilling programme is set up with the limitation which one knows in advance will come which are incurred by the particle size distribution becomes wrong, that is, too coarse due to open holes (h) in lesser or larger proportions in the screen cloths. This incurs that the drilling process is not as good as would otherwise have resulted if the particle size distribution according to the filters used and their nominal values were actually achieved.
The screen cloths' properties throughout the drilling process according to current practice are not registered. Thus the actual temporal development of the cut point of the screen cloth is unknown, and thus also not the quality of the primary separation of the drilling liquid. As an example of through flux by different cut point sizes one may envisage a screen cloth with a cut point of D50 74 μm with a backing of coarser support cloth of D50 1300 μm, such as illustrated in
In summary, the above problems incurred damaged screen cloth in relation to the quality of the resulting drilling mud, particles of too large size are allowed through the damaged shaker screen. Further, the amount of liquid containing too large particle size distributions is larger in proportion than the proportion of damaged screen cloth of the shaker screen.
Another significant problem in that holes are formed in the screen cloth is, that if the screen cloth by a given number of defect cells have open holes, the shaker screen frame must be disposed of and replaced. A shaker screen on a frame costs about 800 US$ and may be consumed in large numbers during a drilling operation of one well. It is difficult to repair a shaker screen on the drilling location if the shaker screen within an entire cell is torn up, but small holes which comprise less than the size of one cell, may be sealed with glue or flexible cement and thus prevent further damage. However, according to the knowledge of the inventor, no system exists which systematically handles problems related to open holes in screen cloths, or any apparatus for automatically repairing screen cloth damages, nor any systematic method for registering the individual histories of used screen cloths during one or more drilling operations. Repair of screen cloths according to present practice is done to a varying degree on the drilling location by use of particularly adapted plugs, glue (single and composite), or silicone based flexible mass. The mending task may constitue a health risk to the operator. The excess man hours required while drilling the larger dimensions such as 24 inches and 17.5 inches may be between 4 and 8 hours in order to keep pace with the development of screen wear while drilling about 3 m3 of rock mass volume per used shaker screen. The upstream face of the screen cloth (1) is worn due to the impacting or migration of cuttings and particles, but also the downstream face of the screen cloth (1) is worn. The downstream face is worn due to grinding by particles but also due to grinding against the support screen (11) within the cell frames (22) which is vibrated against each other. Empirically one knows that the screen cloth takes place from both sides of the screen cloth (1) both in that a wear by particles occurs on the free upper surface of the screen cloth (1) and due to wear from the support cloth (11) or the frame cell's (22) sub-frame (23) against the underside of the screen cloth's surface, until one or more wires in the screen cloth (1) breaks.
Screen cloths, problems related to such screen cloths and their wear, and embodiments of the invention as such are illustrated in the attached drawings. The drawings are meant to illustrate the invention but not to limit the invention.
The invention comprises an apparatus for cleansing screen cloths (1) and monitoring wear of such screen cloths (1), comprising:
A feeding device (100) is arranged for feeding in used or dirty screen cloths (1) or screen cloth frames (2) to a cleansing unit (4). The screen cloths (1) are usually made of steel mesh but may be made in other materials such as composite fibre cloths. The feeding unit may comprise actuators, sheaves and guide rails arranged for displacing and guiding frames (2) with screen cloths (1) from a stack (3) to the cleansing unit (4). The cleansing unit is arranged for receiving and cleansing the screen cloth (1). The aparatus comprises a preparation unit (140), preferably an air blower dryer, arranged for preparing the screen cloth (1) for optical inspection in an optical station described below. the dryer may comprise a fan or a pressurized-air nozzle arranged for blowing air onto the screen cloth. Alternatively, the inspection or the photographic image capture may take place with the screen cloth submerged in a tank with transparent liquid so as for avoiding having to dry the screen cloth before the inspection.
The optical inspection station (120) for the screen cloth (1) may be manual or automatic. In the automatic embodiment of the invention the inspection station is arranged for identifying one or more damaged portions (6) of the screen cloth (1), and registration of one or more of the damaged portions (6) position (7, 7x, 7y). In a preferred embodiment of the invention the optical inspection station (120) comprises a measurement device (62) for measuring and registration of the extent and possible degree of damage of one or more of the damaged portions (6). A subsequently arranged repair unit (70) is arranged for patching or mending one or more of the damaged portions (6) and possibly for registering the extent of the so repaired previously damaged portions (6, 60). The registration of the repaired portions extent may also take place by a post check in the optical inspection station (120).
The invention comprises in a preferred embodiment a feeding out device (200) for feeding out the repaired screen cloth (1) from the repair unit (70), possibly indirectly via the inspection station (120) to a stack station (30) with a stack (3) comprising cleansed, repaired and checked screen cloths (1). In a preferred embodiment of the invention these fed out screen cloths' repaired portions and new properties are registered together with an identifier associated with the screen cloth (1), preferrably in an identifier tag in the frame (2). The screen cloth may also be so-called “frameless”, i.e. that the screen cloth (1) may be arranged for being attached in the vibrating shaker apparatus along two or more edges (8), e.g. by so-called “hook strip”-edges, please see
In a preferred embodiment of the method according to the invention the screen cloth (1) is fed in from a stack station (3) of such screen cloths (1). After cleansing, inspection, registering and repair, the screen cloths are fed out to a stack (30) of such screen cloths (1), preferably to the same stack station (3) from which the used, contaminated screen cloths were stored initially. In this way the clean, repaired screen cloths (1) will reappear in the same stack station which they were stacked into the apparatus. An indicator device in the apparatus may indicate which screen cloths which are useful for further mud filtration and separate those from such screen cloths which should be disposed, by marking or displacing useful screen cloths from disposable screen cloths, or feed out screen cloths to be disposed separately to a separate feed-out stack.
In a practical embodiment of the apparatus according to the invention the optical inspection station (120) is arranged for an operator to conduct the inspection of the screen cloth (1) with the eye, and forther be arranged so as for enabling the operator to conduct a manual measurement of the one or more damaged portions (6) extent and position (7), and register this information. The position (7) may comprsie two coordinates (7x, 7y) which are orthogonal. According to the invention the manual measurement of the one or more damaged portions (6) extent be conducted by means of a so-called hole template (62m) such as is illustrated in
Such data may then be registered together with the borehole depth or the drilling interval during which the screen cloth (1) has been used, and the identifier of the screen cloth, such that one may monitor the development (or degradation) of the screen cloth (1) during the drilling process. Carriers for such identifiers may be such as an RFID-tag (which is known per se) which may be arranged on the frame (2) or otherwhere in connection with the screen cloth (1), said RFID-tag being arranged for following along with and identify the screen cloth (1) on demand from corresponding RFID-equipment arranged in apparatuses in which the screen cloth (1) passes. Possibly the RFID-tag may store data about the screen cloth (1) and its frame (2) and the condition of the screen cloth (1). One may take the screen cloth (1) out of the critical line of use if its actual cut point or actual particle size distribution no longer satisfies given criteria.
The invention comprises in a preferred embodiment an automatic apparatus as illustrated in
The camera (12) may be an area camera capturing the entire or part of the area of the screen cloth (1), or a line camera arranged for scanning line by line of the screen cloth and reconstructs an image of the area of the screen cloth (1) in the camera memory (14) or in an algorithm for reconstructing the image in a computer memory (9). In a preferred embodiment of the invention the algorithm for the registration under step (c) with registering of the one or more damaged portion's (6) position and step (e) registering of the one or more damaged portions (6) extent and degree of damage make the calculations in the computer and the registration of the calculated data to the computer memory (9).
The algorithm may generally identify intact screen cloth (1) and cell frame, either based on colour, grey tone or even actual optical measurement or image analysis of the image to get hold of the mesh size or wire thickness if the camera resolution is sufficiently high. Departures from intact screen cloth (1) will be a worn screen cloth (1) or an open wear hole, identified e.g. by finding an area and intensity of entirely or partly visible coarse mesh support cloth (11) in or behind the screen cloth (1). The algorithm may work with detecting and calculating the limits of worn portions and wear holes. The apparatus' algorithm for measuring and registering of the one or more damaged portions (6) degree of wear may also be arranged for calculating the degree of damage of the damaged portion (6) and possible broken cloth. The algorithm may further be arranged for calculating the cut point curve or particle size distribution after the repair has been made.
The method according to the invention may in a preferred embodiment comprise measurement of the damaged portion's (6) extent and shape in the form of measuring of the damaged portion's (6) diameter or area, and if required also the shape of the damaged portion's (6) circumference. According to a preferred embodiment of the method under item (c) with registration of the one or more damaged portion's (6) position (7) and (e) registration of the one or more damaged portion's (6) extend and degree of wear or damage, the measurements will be conducted and sent directly or indirectly to a computer memory (9) for storage. These data may be stored so as for being related to a frame number or other identifier for the frame (2) and real time well data such as the actual drilling depth interval. In a preferred embodiment of the invention these data may be stored using the RFID-equipment above.
In a preferred embodiment of the invention the apparatuses' cleansing unit such as mentioned under step (b) arranged for cleansing of the screen cloth (1), is provided with a nozzle (43) arranged for flushing cleansing liquid or steam towards at least the upper and preferrably also the lower face of the screen cloth (1) or shaker screen frame (2) with screen cloth (1). In practice the drilling liquid which is released from the screen cloths also have to be flushed away from the inner face of the enveloping cleansing station. The cleansing station may be arranged for arranging the screen cloth (1) or shaker screen frame (2) in an inclined positon, such as illustrated in
As illustrated in
According to the invention the process for cleansing, repair and registration of the finally repaired screen cloth (1) for monitoring wear of the screen cloth (1) is conduced by:
In a preferred embodiment of the method according to the invention one may during one or more steps (f) with repairing one or more of the damaged portions (6) and registering of the repaired portions (60) patched or otherwise repaired or replaced areas, as the patch may comprise screen cloth, measure and register the area of the repaired portions (60) patched or replaced area (both from the current process and from previous repair processes conducted on the same screen cloth (1) or shaker screen frame (2), and thus calculate the remaining, intact proportion of the screen cloth (1). When these data are registered together with the screen cloth's (1) or shaker screen frame's (2) frame number or other identifyer, together with the actual drilling depth interval drilled, lithology, etc., obtain an insight into the screen cloth's (1) drilling history and development of its properties such as cut point and PSD over time, and may relate those to the drilling progress. The operator may futher have an indication to how long the shaker screen may last during its use in the separator during the drilling process. Based on this information and the history of comparable screen cloths (1) or shaker screen frames (2) the operator will obtain good indication to how long the screen cloth may last and at what point of run-time it should be taken out of use for a new general repair or scrapping. The method may during step (f) with registration of the repaired portions (60) extent register real-time data from the drilling process, such as in which time interval the damage (6) occurred, or which drilling depths in the well that the screen cloth (1) has been used when the damage occurred, the circulation rate, the rotational speed for the drill string, the weight on bit, and the rock type. As such the method of the present invention may provide valuable data for higher order drilling monitor processes on the drilling platform so as for enhancing the drilling progress.
In the method according to the invention it may be advantageous, for the step of measuring and registering the repaired portions (60) state and exent, to transfer the screen cloth (1) to the optical inspection station (120) such as indicated in
The apparatus according to the invention is, in other words, an industrial washing machine for relatively fine mesh screen cloths (1) used for separating drill cuttings from drilling liquid or driling mud during a well drilling process. The drilling process may use rather low density drilling slurry-like liquids such as early after setting the riser and the BOP, or higher density drilling liquids such as used when high well pressure may be encountered. The machine according to the invention is arranged for washing and drying screen cloths (1), for inspecting for wear and damage, for repairing possible damages or holes, for inspecting the screen cloth after possible repairs, and in a preferred embodiment for storing the repair data and relate those data to the identifier of the screen cloth's frame number and the actual drilling depth interval of use, and for returning the cleansed, possibly repaired screen cloth for further use.
Thus the apparatus and the method according to the invention may contribute not only to clean screen cloths used in the drilling process, but also for detecting wear and damage at a given time during the drilling process, measure the extent of the damage, repair the damage to an acceptable degree before the extent of the damage may increase to an undesired degree or in an uncontrolled manner, and possibly take out shaker screens which no longer may contain or separate the drilling liquid in a proper way. During drilling processes using screen cloths in the way used in industry practice a rough estimate of the duration of a shaker screen may be about 3 m3 theroretically drilled well volume per shaker screen before it has been afflicted 20% damage or reduction of its capacity.
In a drilling process which has been conducted using a manual experimental embodiment of the method according to the invention, in which systematic observation, measurement and registration of wear and open holes of the screen cloths have been conducted, and in which open holes have been repaired, and in which an account has been made over the screen cloths' remaining intact area, the duration of a number of 25 applied screen cloths have been increased to about 1200 m3 filtered, theroretically drilled out well volume per shaker screen frame, and no screen frames had to be disposed of. In this way the invention to a large degree solves the problems of the background art related to wear and damages to screen cloths, and contributes significantly to reduction in the consumption of screen cloths during drilling petroleum wells. The method and the apparatus according to the invention contributes to actually register the real conditions related to the actual cut point and PSD for the controlled and repaired screen cloths and thus the quality of the primary separation, which in the bacground art is not actually taken care of. Indirectly the apparatus and the method of the invention reduces the wear of the shaker screen and may thus contriubute to improve the drilling progress and increase the degree of predictability to complete the predefined drilling schedule within a given time and budget.
| Number | Date | Country | Kind |
|---|---|---|---|
| NO20084021 | Sep 2008 | NO | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/NO2009/000329 | 9/22/2009 | WO | 00 | 3/31/2011 |
| Number | Date | Country | |
|---|---|---|---|
| 61099113 | Sep 2008 | US |
