Patent Application
20190383110
The present invention relates to filter screen assemblies used to filter drilling mud of the type used in downhole drilling technologies in the oil and gas industries and to a method for installing such a filter screen assembly in a well bore drilling operation.
The “mud” circulating system is used to circulate drilling fluid down through the drill string and up the annulus, carrying the drilled cuttings from the face of the bit to surface and will be familiar to those skilled in the relevant arts. Among the main functions of the circulating drilling fluid are to clean the borehole of cuttings made by the drill bit, to cool the drill bit head, and to exert a hydrostatic pressure sufficient to prevent formation fluids from entering the borehole.
Drilling fluid (mud) is usually a mixture of water, clay, weighting material, such as barite, and chemicals. The mud is mixed and conditioned in mud pits or tanks located at the well surface and is then circulated downhole by large pumps. These pumps are typically present at the ground level, for example, adjacent the rig floor or at subfloor or substructure of the rig. These are typically reciprocating positive displacement pumps, for example Triplex Pumps™. These types of pumps are well known in the industry and are often used because they can operate over a wide range of pressure and pump fluids containing high solids content and tend to be relatively reliable and easy to operate and maintain.
In the case of a typical drilling rig, the mud is pumped through, for example, a standpipe, rotary hose, a swivel, and a Kelly and then down the drill string. At the bottom of the borehole, the mud passes through the bit and then up the annulus between the drill string and surrounding well bore, carrying cuttings up to surface. On surface the mud is directed from the annulus, through a mud return line back to the mud tanks and ultimately back to the mud pumps. However, before it re-enters the mud tanks, the drilled cuttings are removed from the drilling mud by some of solids removal equipment. The used mud may also be reconditioned in other ways.
Once the drilled cuttings have been removed from the mud it is re-circulated down the borehole. The mud is therefore in a continuous circulating system. The properties of the mud are checked continuously to ensure that the desired properties of the mud are maintained. If the properties of the mud change then chemicals will be added to the mud to bring the properties back to those that are required to fulfill the functions of the fluid. The chemicals may be added, for example, while the drilling fluid is being circulated through the mud tanks.
As has been mentioned, during drilling operations as the mud is being circulated, it begins to accumulate suspended drilled cuttings, as well as some gas or other possible contaminants. These must be removed before the mud is recycled. In a typical operation, the mud passes over a shale shaker, which is basically a vibrating screen. This will remove the larger particles, while allowing the residue (underflow) to pass into settling tanks. The finer material can be removed using other solids removal equipment. If the mud contains gas from the formation it will be passed through a degasser which separates the gas from the liquid mud. Having passed through all the mud processing equipment the mud is returned to the mud tanks for recycling.
The debris which the drilling mud picks up can affect the flow of the mud and the operation of the drill bit and other tools. In addition to the mud conditioning equipment previously described at the well surface, in the past, a filter screen subassembly was often installed in the drill string to help collect and filter debris. Downhole filter screens are run, for example, during directional drilling operations and are sometimes installed near the drill bit at the bottom of the drill string, and thus are not easily accessible during drilling. In some cases, to remove or clean out a downhole filter screen, the entire drill string must be pulled out of the wellbore.
U.S. Pat. No. 6,598,685, issued Jul. 29, 2003, to Mashburn, is a typical prior art drilling system in which a down hole filter screen is used. As described in the patent, a filter screen is placed within the box end of a tubular member by a worker located in the monkey bars of the derrick. A kelly top drive is attached to the tubular members so that the drilling of a bore hole with the drilling bit may proceed. In the case of a top drive, the top drive and tubing string is lowered by the derrick draw works as drilling proceeds. The operator has the option of retrieving the screen from the rig floor before coupling the tubular to another tubular joint. The screen can also be kept within the drilling tubular as a second joint of drilling tubular is threadedly connected in the string.
Once the drilling tubulars are to lowered into the well bore, the filter screen can no longer be removed by hand since the drilling tubulars are now threadedly coupled together. When it is desired to retrieve the screen, a wire line unit is used to retrieve the screen with a special pulling tool. The pulling tool would latch onto a fishing neck of the screen and the filter screen would then be pulled from the drilling tubulars to the well surface.
The above described procedure is time consuming and somewhat complicated. Also, prior art downhole filter screens can be damaged during drilling operations. Filters in the drill string are subject to washing. Also, if a filter screen fills with debris and is not properly maintained or cleaned, then it can cause blockages in the fluid flow or other problems. In some extreme cases, the filter screen may shear off due to excess debris buildup or excess vibration during drilling operations. The broken filter screen can be pushed by the fluid flow of the drilling mud and may end up at the bottom of the borehole. Due to the inconveniences from factors such as installation, cleaning, and maintenance, filter screens are sometimes not used by drilling operators despite the benefits they provide in filtering drilling mud.
Because of these kinds of problems with downhole filter screens, surface pipe screens are also sometimes used to filter drilling mud. In the past, these pipe screens were typically installed in the drill string above the surface, typically at an elevated position on the drilling rig, and they are designed to catch finer particulates than downhole filter screens. They may be part of a top drive, for example, or in close proximity to the top drive, at an elevation located above the rig floor.
U.S. Pat. No. 6,976,546, issued Dec. 20, 2005, to Herst, is a typical prior art drilling mud filtration system using a filter screen which is disposed within a drilling mud fluid passageway that extends from the entry point of the drilling mud into the overhead drilling system on the top drive unit. Specifically, the overhead drilling system includes a washpipe assembly, having a gooseneck extending therefrom for receiving an S-pipe and the mud filter screen is disposed within the S-pipe. The S-pipe is located immediately adjacent the upper end of the top drive unit at an elevated position on the drilling rig.
These prior art surface filter screen systems also suffer from various disadvantages. In the case of some of the prior art top drive arrangements, each time a new drill pipe segment is ready to be added to the drill string, the top drive must be disconnected from the drill string. Before connecting the new drill pipe segment, the installed surface pipe screen must be removed from the topmost box end of drill pipe in the drill string. After the new drill pipe segment is connected to the drill string, the surface pipe screen can be reinstalled into the new drill pipe segment's box end, and the top drive can be reconnected with the drill string. If the surface pipe screen is ever forgotten when adding new segments of pipe, the surface pipe screen may become “lost” in the drill string, making its retrieval difficult and tedious. Further, if a surface pipe screen ever shears off, it may become lodged along with debris anywhere in the drill string.
Additionally, the traditional surface pipe screens installation which were installed on the top drive or adjacent the top drive had the potential to present safety issues Many drilling operators enforce a safety zone around the drill string when the top drive is disconnected from the drill string. In some cases, operators forgo the use of surface pipe screens, rather than risk the safety of personnel during the frequent insertion and removal of a surface pipe screen during drilling operations.
Accordingly, there exists a need for the safe and easy attachment and removal of a filter screen assembly that overcomes many of the problems described with respect to the prior art filter screens.
The following invention presents a novel design for a filter screen assembly used in a variety of different conventional mud circulation systems of the type used on oil and gas well drilling rigs. The filter screen assembly is installed at the surface of a well on the discharge side of the mud pump typically at ground level, for example, as a part of the substructure of the rig. It does not need to be removed and reinstalled when additional segments are added to the drill string and is always easily accessible for routine maintenance or replacement. Since it is located at ground level, it does not present the safety hazards that some of the prior art arrangements presented where filtering devices were placed at elevated locations on the drill rig.
A method of drilling a well bore is shown which uses the improved filter screen assembly of the invention, where drill bit cuttings and other abrasive debris and contaminants are filtered from a drilling mud that is circulated from a surface mud tank through an oil or gas well drilling system. The filtering system is located on a well drilling rig having a rig floor and a rig derrick, the method comprising the steps of:
The drilling rig may be provided with a stand pipe that is located in the interconnecting conduit between the discharge outlet of the mud pump and the remainder of the drill string on the derrick, the stand pipe being positioned in a generally upright position in the derrick. In this case, the filter screen assembly used in the method of the invention will be positioned in the interconnecting conduit adjacent the discharge outlet of the mud pump at a surface level on the rig floor or floor substructure and prior to the stand pipe. In any case, the filter screen assembly will be located at ground level, for example, as a part of the substructure of the rig.
The mud filter screen assembly may assume various configurations, but will in any case be a porous structure, typically made of metal, having a plurality of openings along a length thereof which allows a flow of drilling mud through the filter screen portion of the assembly, while trapping drill bit cuttings, shavings and other abrasive debris. For example, the filter screen porous structure may be selected from the group consisting of metal mesh material, a plurality of welded metal bars, or a generally solid metal tube having a plurality of longitudinal opening formed therein. The filter screen porous structure could also be made from a variety of synthetic materials such as Nylon or various hard plastics.
Additional features and advantages will be apparent in the written description which follows.
The preferred version of the invention presented in the following written description and the various features and advantageous details thereof are explained more fully with reference to the non-limiting examples included and as detailed in the description which follows. Descriptions of well-known components and processes and manufacturing techniques are omitted so as to not unnecessarily obscure the principal features of the invention as described herein. The examples used in the description which follows are intended merely to facilitate an understanding of ways in which the invention may be practiced and to further enable those skilled in the art to practice the invention. Accordingly, the examples should not be construed as limiting the scope of the claimed invention.
As has been described in some detail in the Background discussion above, in the oil and gas industry, downhole drilling operations may drill boreholes that extend thousands of feet into the ground. Drilling muds are used to facilitate such drilling operations.
The mud is further pumped through a drilling mud fluid passageway (internal bore) of the drill pipe string 27 to a bottom hole assembly and drill bit 33. In the simplified view shown in
As has been mentioned, prior art drilling systems often employed a filter screen assembly in addition to the shale shakers, vibrating screen, etc., present at the well surface, to further filter the recirculating drilling mud. These filter screens were typically placed either in the drill string, or in an elevated position on the drilling rig, as for example, being incorporated into some part of a top drive assembly or adjacent to such an assembly. In any event, the filter screen assemblies were located above the rig floor or within a section of the drill pipe itself. The various disadvantages that result from such an arrangement have been discussed.
In the method of the present invention, a drilling system such as the system shown simplified fashion in
Unlike the prior art systems, in the method used in the present invention, the filter screen assembly (49 in
In the preferred embodiment shown in
The length of the filter screen itself terminates in an end cap 65 having a plurality of end openings 67.
The coupling members, such as member 83 can be traditional “hammer unions” of the type that will be familiar to those skilled in the relevant arts. As best shown in
During drilling operations, used mud returns to the mud tanks 15 through a return line (93 in
An invention has been provided with several advantages. The filter screen system of the invention has the ability to put the filter screen on the discharge side of the mud pump, thereby eliminating the need for other types of filter screens such as top drive screens, surface screens, downhole filters, and the like. Unlike the filter screens presently offered in the marketplace, the present system is not tied to a specific rotary connection size and would eliminate that need. The prior art systems typically require removal and reinsertion on every stand of pipe, and this need would be eliminated by the present system. The present system can be utilized with any of a number of drilling rigs with the screen assembly simply being placed in-line in the mud circulation system. It stays with the drilling fluid system which is specific to the drilling rig at hand.
