Patent Application
20170204695
The disclosure relates generally to extending the reliability of blowout preventers.
Oil and gas field operations typically involve drilling and operating wells to locate and retrieve hydrocarbons. Rigs are positioned at well sites in relatively deep water. Tools, such as drilling tools, tubing and pipes are deployed at these wells to explore submerged reservoirs. It is important to prevent spillage and leakage of fluids from the well into the environment. A significantly large pressure kick can result in a “blowout” of drill pipe, casing, drilling mud, and hydrocarbons from the wellbore, which can result in failure of the well.
Blowout preventers (“BOPs”) are commonly used in the drilling and completion of oil and gas wells to protect drilling and operational personnel, as well as the well site and its equipment, from the effects of a blowout. In a general sense, a blowout preventer is a remotely controlled valve or set of valves that can close off the wellbore in the event of an unanticipated increase in well pressure. Modern blowout preventers typically include several valves arranged in a “stack” surrounding the drill string. The valves within a given stack typically differ from one another in their manner of operation, and in their pressure rating, thus providing varying degrees of well control. Longevity and reliability of BOPs is critical for safe functioning of oil wells.
A typical BOP stack is made up of several ram preventers, topped off with an annular preventer. If a kick is detected, the annular BOP is usually closed first and then the ram is used as a backup if the annular BOP should fail. Multiple blowout preventers of the same type are frequently provided for redundancy, to ensure effectiveness of fail-safe devices.
Typically BOP packers comprise elastomeric polymers which are subject to high pressures and high temperatures in the field. Exposure of elastomeric seals to extreme high temperatures can cause physical and/or chemical deterioration where the seal will initially soften and then swell causing increased friction in dynamic applications. High pressure applications are also prone to failure because room temperature tests may provide inaccurate results. Over time, irreversible chemical changes occur under high pressure/high temperature that increase seal hardness as well as induce compression set and volumetric changes.
Certain industrial activities, such as oil and gas extraction, have increasingly expanded to subsea locations, as the number of available land-based sites has declined. Subsea wells require BOPs to remain submerged for as long as a year in extreme conditions. As a result, BOP assemblies for subsea wells have grown larger and heavier while the space allotted for BOP stacks on existing offshore rigs has not grown commensurately. Accordingly, there is a need in the field for increasing safe operating capacity and extending the life of the BOPs during oil and gas extraction.
One critical failure mode of conventional BOP packers/seals is cracking under load of high pressure or high temperature (HP/HT) and repeated cycling. In order to improve the longevity and operating range of the existing packers, provided herein are BOP sealers/packer wherein the elastomer matrix in the packers is modified with self-healing characteristics in regions which are susceptible to cracking under load, thereby allowing for in situ healing of the cracks and prevention of degradation of the matrix to the point of failure. Further, the directed sealers/packers described herein are designed in such a way that a self-healing process is triggered only when a crack is propagated, and not during the molding and/or normal operation of the packer.
In one aspect, provided herein are blowout preventers (BOP) comprising
In a further aspect, provided herein are computer-implemented methods for identifying optimized microcapsule diameters, for placement of microcapsules in regions of high stress or high strain in a BOP packer. In yet another aspect, provided herein are computer-implemented methods for identifying regions of high stress or high strain in a BOP packer, and directing placement of at least one self-healing material comprising a polar liquid additive or a microcapsule comprising a self-healing agent thereto.
These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
The BOP 14 is mounted below the one or more annular blowout preventers on an upper end (not labeled in
In certain embodiments, each variable ram 16 may include a ram block and a ram packer assembly disposed at least in part within the ram block. In such embodiments, the ram packer assembly may include a plurality of inserts (not shown in
It should be noted that in a cylindrical coordinate system, reference numeral 34 represents an axial direction of the variable ram 16, reference numeral 36 represents a radial direction of the variable ram 16, and reference numeral 38 represents a circumferential direction of the variable ram 16.
During operation, the drill pipe 26 is configured to rotate along the circumferential direction 38 so as to excavate the wellbore 22 and extract hydrocarbons (fluid) from the reservoirs along the wellhead casing 12. In such embodiments, the extracted fluid from the reservoirs may be transported to a distant fluid storage facility through pipelines coupled to the wellhead casing 12. In some embodiments, during certain transient operating conditions, each of the biasing devices 32 is configured to move a corresponding variable ram 16 out of the housing 28 towards the opening 30. In such embodiments, a bore face 60 (
The ram packer assembly 42 is disposed at least in part within the ram block 40. In one embodiment, the ram packer assembly 42 includes a plurality of inserts 44 and a packer member 46. In the illustrated embodiment, each insert 44 of the plurality of inserts 44 includes a top plate 52, a bottom plate 54, and a central web 56 interconnecting the top plate 52 with the bottom plate 54. In certain embodiments, the plurality of inserts 44 is made of a metal. The plurality of inserts 44 is disposed adjacent to each other to form an insert array 48. In one embodiment, the insert array 48 includes a peripheral surface 50 which is disposed facing an opening 30 configured to receive a drill pipe 26 (as shown in
In one embodiment, the packer member 46 is coupled to at least a portion of the plurality of inserts 44 for providing a unitary or integral structure to the ram packer assembly 42. In certain embodiments, the packer member 46 protrudes from the peripheral surface 50 of the insert array 48 into the opening 30 to define a bore face 60 of each variable ram 16. Specifically, the packer member 46 protrudes inwardly towards the opening 30 along a radial direction 36 of the variable ram 16. Further, the packer member 46 extends along a circumferential direction 38 of the variable ram 16.
In one embodiment, the ram packer assembly 42 further includes a pair of wing seals 62, a packer side seal 64, and a pair of pins 66. The packer side seal 64 is coupled to another peripheral surface 70 of the insert array 48, disposed opposite to the peripheral surface 50. Each wing seal of the pair of wing seals 62 is coupled to a corresponding peripheral side of the ram packer assembly 42. Each pin of the pair of pins 66 is coupled to a corresponding wing seal of the pair of wings seals 62. In such embodiments, the ram packer assembly 42 is disposed at least in part in the ram block 40 and coupled to the ram block 40 via the pair of pins 66 and a corresponding pair of slots (not shown in
Elastomeric packers/sealing elements in blowout-preventers (BOPs) are used to seal around various pipe sizes. The variable ram packer consists of metallic inserts and elastomers that work as a coherent unit to create a seal. The elastomers that are currently used in the field undergo large deformations across the bore face, face recess and other critical regions during operation. The deformations result in a breakdown of the material that eventually leads to failure. In addition to the BOP packers, other high pressure high temperature (HP/HT) seals also have a number of failure modes related to cracking, such as rapid gas decompression and fatigue, leading to a lack of reliable sealing under HP/HT conditions.
Provided herein are methods for improving the reliability of packers and sealers including HP/HT sealers and BOP sealers/packers. The methods involve directing elastomeric materials with self-healing properties to specific areas in BOP packers which are susceptible to stress and cracking. The directed compositions described herein allow for cracks to be healed as soon as they are formed, thereby improving the reliability and application space of packers and seals, including BOP packers and HP/HT seals.
As used herein, in one embodiment, the term “elastomer” or “elastomeric” encompasses thermosets (e.g., polymers requiring vulcanization). In a further embodiment, the term “elastomer” or “elastomeric” encompasses thermoplastics. In yet another embodiment, the term “elastomer” or “elastomeric” encompasses a mixture of one or more thermosets and one or more thermoplastics. In one group of embodiments, any elastomer-based packer described herein is comprised of one or more of nitrile-butadiene rubber (NBR), hydrogenated nitrile butadiene rubber (HNBR), carboxylated nitrile butadiene rubber (XNBR), fluoroelastomers (FKM), perfluoroelastomers (FFKM), natural rubber (NR), and the like, or combinations thereof. In another group of embodiments, examples of the elastomeric material may include rubber, neoprene, nitrile rubber, hydrogenated nitrile rubber, carboxylated nitrile rubber, natural rubber, butyl rubber, ethylene-propylene rubber, epichlorohydrin, chlorosulfonated polyethylene, fluoroelastomers, and the like, or combinations thereof.
As used herein, “regions of high stress or high strain” in a BOP packer are typically determined using finite element analysis (FEA). For the purpose of this disclosure, the regions of strain in a packer during the operation of the BOP are classified from FEA as regions of strain comprising >90% of maximum strain for elongation at break (and noted as regions of large strain in the accompanying figures); regions of strain comprising >40% of maximum strain for elongation at break (and noted as regions of medium strain in the accompanying figures); and regions of strain comprising <40% maximum strain for elongation at break (and noted as regions of small strain in the accompanying figures). Accordingly, “regions of high strain” in a packer comprise regions of strain comprising at least >40% of maximum strain for elongation at break based on FEA; and preferably comprise regions of strain comprising >90% of maximum strain for elongation at break based on FEA. Such regions have a higher probability of cracking/tearing during the operation of the BOP. Although the accompanying figures only show FEA for regions of high strain, it will be understood that a corresponding analysis can be conducted to identify regions of high stress.
As used herein, “processing conditions encountered during compounding of the packer and during normal operation of the packer” relate to typical temperatures and pressures during compression molding of the packer. Strains induced in the elastomeric packer by these conditions would not crack any microcapsules described herein and would not trigger any healing of the elastomer by any liquid additive described herein. Typical temperatures during compression molding of the packer may vary from about 100 deg. C. to about 210 deg. C., although other temperature ranges are possible and are expressly contemplated herein as being within the scope of embodiments described herein. Typical pressures during compression molding of the packer may vary from about 90 psi to about 110 psi, although other pressure ranges are possible and are expressly contemplated herein as being within the scope of embodiments described herein.
As used herein, “crack-propagating conditions in the elastomer” refers to conditions which impose higher than normal stress/strain in the BOP packer. During normal operations, the BOP packers are typically subjected to a temperature range of about 0 deg. C. to about 177 deg. C. under about 15-20 ksi pressures. Under these conditions, the microcapsules in the elastomer would not break open by themselves, and the liquid additive would not trigger healing of the elastomer. However, the combination of high temperatures (HT) and high pressures (HP) along with cyclic loading can trigger cracks in the elastomeric packer. For example, microcracks from which failure of the BOP can originate may arise from slippage between polymer chains producing reorientation where the chains acquire a state of tension. Subsequently, local scission occurs which then propagates to neighboring chains causing cracks that propagate irreversibly. Under such crack propagating conditions, the microcapsules would break open and initiate healing of the elastomer, or, the liquid additive would initiate healing of the elastomer.
Accordingly, in a first aspect, provided herein are blowout preventers (BOP) comprising
In one group of embodiments, the self-healing material is directed to regions of high stress in the packer. In another group of embodiments, the self-healing material is directed to regions of high strain in the packer.
In one group of embodiments, the BOP comprises a variable bore ram packer.
In some embodiments, the regions of high stress or high strain in a variable bore ram packer are one or more of
In one group of embodiments, the regions of high stress or high strain in a variable bore ram packer are shown in
In another group of embodiments, the BOP comprises an annular packer.
In some embodiments, the regions of high stress or high strain in an annular packer are one or more of
In one group of embodiments, the regions of high stress or high strain in an annular packer are shown in
In yet another group of embodiments, the BOP comprises a fixed bore ram packer. In certain embodiments, the regions of high stress or high strain in a fixed bore ram packer are identified using methods similar to the methods described herein and are suitable for directing the placement of self-healing materials described herein.
In some embodiments, the self-healing material comprises a self-healing agent encapsulated by a coating material defining a microcapsule, the coating material of the microcapsule being stable at processing conditions encountered during compounding of the packer and during normal operation of the packer, yet, unstable under crack-propagating conditions in the elastomer.
In some embodiments, the self-healing agent comprises a thermosetting polymer. In some of such embodiments, said self-healing agent comprises a nitrocellulose cement, a cyanoacrylate adhesive, an epoxy based adhesive, an aliphatic polyurethane, an isocyanate terminated aliphatic urethane prepolymer, or dicyclopentadiene (DCPD), or a combination thereof.
In some other embodiments, the self-healing material comprises a polar liquid additive. In some of such embodiments, the polar liquid additive comprises polyethylenimines (PEI).
In one group of embodiments, said elastomeric packer comprises nitrile-butadiene rubber (NBR), hydrogenated nitrile butadiene rubber (HNBR), carboxylated nitrile butadiene rubber (XNBR), fluoroelastomers (FKM), perfluoroelastomers (FFKM), or natural rubber (NR), or a combination thereof.
In one group of embodiments, where the self-healing material is a self-healing agent encapsulated by a coating material defining a microcapsule, the coating material of said microcapsule comprises a urea-formaldehyde polymer, an epoxy, a silicone, or a combination thereof.
Also provided herein is a method for increasing the life of a blowout preventer (BOP) comprising
Further provided herein is a computer-implemented method for identifying an optimized microcapsule diameter, for placement of microcapsules in regions of high stress or high strain in a BOP packer, comprising
Also provided herein is a computer-implemented method for identifying regions of high stress or high strain in a BOP packer, to direct placement of at least one self-healing material comprising a polar liquid additive or a microcapsule comprising a self-healing agent, comprising:
In a typical blowout preventer, sheets of elastomer are positioned between metallic inserts and then the elastomeric sheets are subjected to the process of transfer or compression molding. In accord with the methods described herein, sheets of elastomers are replaced with sheets of self-healing elastomers in the regions of high strain or high stress as described herein. Alternatively, elastomer is injected in the packer assembly. In accord with the methods described herein, elastomers which are injected are replaced with self-healing elastomers in the regions of high strain or high stress as described herein.
In addition to maintaining integrity during normal well operations and/or a “kick”, the presently described BOPs comprising modified elastomers in the packer are also useful for sealing against the drill pipe during a “stripping” operation. During a stripping operation, the drill pipe is pulled from the well bore with the blowout preventer closed against the drill pipe. This results in wear and tear on the ram packer, particularly the elastomeric sealing element. Accordingly, also contemplated within the scope of embodiments presented herein is the use of the presently described BOPs during said stripping operations. Further contemplated within the scope of embodiments presented herein is the use of the BOPs comprising modified elastomers in the packer to regulate and monitor wellbore pressure; shut in the well (e.g. seal the void, annulus, between drill pipe and casing); “kill” the well (prevent the flow of formation fluid, influx, from the reservoir into the wellbore); seal the wellhead (close off the wellbore); or sever the casing or drill pipe during an emergency. U.S. application Ser. No. 14/964,639 describes certain blow out preventers having a modified design, which disclosure is incorporated herein by reference, and such blow out preventers are also contemplated for modification of elastomers therein using the methods and compositions provided herein.
Also contemplated within the scope of embodiments presented herein are seals/packers in general (e.g., elastomer based seals/packers), wherein regions of high stress and/or high strain can be identified using the methods described herein and said seals/packers can then be modified with self-healing material directed to regions of high stress and high strain as described herein.
In
In
In
HNBR matrix modified with the microcapsules were subjected to the conventional compounding process (i.e. compression molding). The scanning electron micro-graph in
While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.
