This invention relates, in general, to completing a wellbore that traverses one or more subterranean hydrocarbon bearing formations and, in particular, to a system and method for completion optimization using a computer implemented system and method to dynamically modeled the service tool string and the downhole environment.
Without limiting the scope of the present invention, its background is described with reference to the production of hydrocarbons through a wellbore traversing unconsolidated or loosely consolidated formations, as an example.
It is well known in the subterranean well drilling and completion art that particulate materials such as sand may be produced during the production of hydrocarbons from a well traversing one or more unconsolidated or loosely consolidated subterranean formations. Numerous problems may occur as a result of the production of such particulate. For example, the particulate causes abrasive wear to components within the well, such as tubing, pumps and valves. In addition, the particulate may partially or fully clog the well creating the need for an expensive workover. Also, if the particulate matter is produced to the surface, it must be removed from the hydrocarbon fluids by processing equipment at the surface.
One method for preventing the production of such particulate material to the surface is gravel packing the well adjacent the unconsolidated or loosely consolidated production interval. In a typical gravel pack completion, a completion string including a packer, a circulation valve, a fluid loss control device and one or more sand control screens is lowered into the wellbore to a position proximate the desired production interval. A service tool is then positioned within the completion string and a fluid slurry including a liquid carrier and a particulate material known as gravel is then pumped through the circulation valve into the well annulus formed between the sand control screens and the perforated well casing or open hole production zone.
The liquid carrier either flows into the formation or returns to the surface by flowing through the sand control screens or both. In either case, the gravel is deposited around the sand control screens to form a gravel pack, which is highly permeable to the flow of hydrocarbon fluids but blocks the flow of the particulate carried in the hydrocarbon fluids. As such, gravel packs can successfully prevent the problems associated with the production of particulate materials from the formation. During certain gravel packing operations in well having multiple zones, the service tool used to deliver the gravel slurry may be positioned relative to each of the zones to be completed in a single trip. For example, the service tool is typically first positioned relative to the lowermost zone to perform the first gravel packing operation then lifted uphole to sequentially perform gravel packing operations on the next uphole zone until each of the zones is gravel packed. It has been found, however, that such axially movement of the service tool relative to the completion string lacks precision and certainty regarding the exact location of certain service tool components relative to particular landing points within the completion string. Specifically, the service tool is repositioned by raising and lowering the block at the surface, which is typically thousands of feet away from the downhole landing points of the service tool. The distance the block is moved at the surface, however, does not directly translated to the distance the service tool moves downhole. For example, movement of the service tool is effected by both static and dynamic frictional forces, gravitational forces, pressure forces and the like. This is particularly acute in slanted, deviated and horizontal wells. In addition, the length of the service tool string is not constant due to thermal effects, particularly in deep-water completions.
Therefore, a need has arisen for systems and methods for completing a wellbore that traverses one or more subterranean hydrocarbon bearing formations that enhance the precision and certainty regarding the location of the service tool relative to a particular landing point or landing points within the completion string. A need has also arisen for such systems and methods that are able to correlate between the distance the block is moved at the surface and the distance the service tool moves downhole. Further, need has arisen for such systems and methods that are able to account for the thermal effects experienced by the service tool string in downhole environments including subsea environments.
The present invention disclosed herein is directed to systems and methods for completing a wellbore that traverses one or more subterranean hydrocarbon bearing formations that enhance the precision and certainty regarding the location of the service tool relative to a particular landing point or landing points within the completion string. The systems and methods of the present invention are able to correlate between the distance the block is moved at the surface and the distance the service tool moves downhole accounting for friction forces, gravitational force, pressure forces and the like. In addition, the systems and methods of the present invention are able to account for the thermal effects experienced by the service tool string in downhole environments including subsea environments.
In one aspect, the present invention is directed to a system for completing a wellbore. The system includes a completion positioned within the wellbore. The completion has at least one landing point defined therein. A service tool is axially movable within the completion. The service tool is coupled to a service tool string extending from the surface and selectively supported by a movable block above the surface. A subsurface model is defined in a computer operably associated with the wellbore. The model is operable to predict the position of the service tool relative to the at least one landing point of the completion based upon a dynamic lumped mass model of the service tool string and a dynamic lumped capacitance thermal model of the wellbore environment.
In one embodiment, the subsurface model includes wellbore design, completion design and service tool design. In another embodiment, the subsurface model is updated with block movement information and hook load information. In one embodiment, the dynamic lumped mass model of the service tool string defines a plurality of axial sections of the service tool string and represents each axial section as a single mass. In this embodiment, a connection between adjacent masses may be represented as a spring and damper. In another embodiment, the dynamic lumped mass model of the service tool string includes frictional forces, gravitational forces and pressure pistoning forces.
In one embodiment, the dynamic lumped capacitance thermal model of the wellbore environment includes a bottom hole temperature and a temperature profile between the bottom hole temperature and a surface temperature. In this embodiment, a linear profile may be applicable in onshore wellbores and for offshore wellbore in the region between the bottom hole and the sea floor with the temperature profile between the sea floor and the rig floor being based upon known temperature profiles for sea water. In another embodiment, the dynamic lumped capacitance thermal model of the wellbore environment includes fluid circulation rate and return fluid temperature. In one embodiment, the dynamic lumped capacitance thermal model of the wellbore environment defines a plurality of axial sections of the wellbore with each axial section being divided into a plurality of annular nodes. In this embodiment, heat transfer between adjacent annular nodes may be represented as resistance.
In one embodiment, the subsurface model includes an auto calibration function that correlates the predicted position of the service tool relative to the at least one landing point of the completion with the actual position of the service tool relative to the at least one landing point of the completion when the service tool sets down in a landing point. In another embodiment, the subsurface model defines a zone of confidence regarding the position of the service tool relative to the at least one landing point of the completion after a predetermined period of time following a predetermined event.
In another aspect, the present invention is directed to a method for completing a wellbore. The method includes positioning a completion within the wellbore, the completion having at least one landing point defined therein, and disposing an axially movable service tool within the completion, the service tool coupled to a service tool string extending from the surface and selectively supported by a movable block above the surface. The method also includes defining a subsurface model in a computer operably associated with the wellbore, the model predicting the position of the service tool relative to the at least one landing point of the completion based upon a dynamic lumped mass model of the service tool string and a dynamic lumped capacitance thermal model of the wellbore environment.
In another aspect, the present invention is directed to a system for completing a wellbore. The system includes a completion positioned within the wellbore. The completion has at least one landing point defined therein. A service tool is axially movable within the completion. The service tool is coupled to a service tool string extending from the surface and selectively supported by a movable block above the surface. A controller is operable to control the movement of the block such that the service tool may be raised and lowered in the wellbore. A subsurface model is defined in a computer operably associated with the controller. The model is operable to predict the position of the service tool relative to the at least one landing point of the completion based upon a dynamic lumped mass model of the service tool string and a dynamic lumped capacitance thermal model of the wellbore environment.
For a more complete understanding of the features and advantages of the present invention, reference is now made to the detailed description of the invention along with the accompanying figures in which corresponding numerals in the different figures refer to corresponding parts and in which:
While the making and using of various embodiments of the present invention are discussed in detail below, it should be appreciated that the present invention provides many applicable inventive concepts, which can be embodied in a wide variety of specific contexts. The specific embodiments discussed herein are merely illustrative of specific ways to make and use the invention, and do not delimit the scope of the invention.
Referring initially to
A wellbore 38 extends through the various earth strata including formation 14. An upper portion of wellbore includes casing 40 that is cemented within wellbore 38. Disposed in an open hole portion of wellbore 38 is a completion 42 that includes various tools such as packers 44, 46, 48, 50 that provide zonal isolation for the production of hydrocarbons in certain zones of interest within wellbore 38. When set, packers 44, 46, 48, 50 isolate zones of the annulus between wellbore 38 and completion 42. In this manner, formation fluids from formation 14 enter the annulus between wellbore 38 and completion 42 between packers 44, 46, between packers 46, 48, and between packers 48, 50. Additionally, gravel pack and fracpack slurries or other treatment fluids may be pumped into the isolated zones provided therebetween.
Completion 42 also includes sand control screen assemblies 52, 54, 56. As shown, packers 44, 46, 48, 50 are respectively located above and below each of the sand control screen assemblies 52, 54, 56. Completion 42 further includes closing sleeves 58, 60, 62 that provided a pathway through completion 42 for the delivery of a fluid slurry into the annulus surrounding the various isolated portions of completion 42 during a treatment process. Closing sleeves 58, 60, 62 each include one or more interior landing points designed to receive various portions of the service tool carried on the lower end of service tool string 36, which is disposed within completion 42 in
Even though
Referring next to
To model these forces, the service tool string, from the travel hook to the completion, is split into a plurality of sections with the mass of each section assumed to be at the midpoint of that section, which is referred to herein as a lumped mass model. Each of the masses is then assumed to be coupled to each adjacent mass by a spring and damper. As depicted in
In constructing the lumped mass model of the service tool string, an equation is created for each mass, such as mass j, which can be expressed as an equation of motion as follows:
m{umlaut over (x)}=−bj({dot over (x)}j−{dot over (x)}j−1)+bj+1({dot over (x)}j+1−{dot over (x)}j)−kj(xj−xj−1)+kj+1(xj+1−xj)−Ff−Fg−Fp−kjα(ΔTj)lj+kj+1α(ΔTj+1)lj+1
Where, b is the axial damping coefficient of the pipe, k is the spring coefficient of the pipe, Ff is the frictional force, Fg is the gravitational force, Fp is the pressure pistoning force, α is the thermal expansion coefficient, ΔT is the change in temperature and l is the length of the pipe section. Once the equation of motion is created for each mass, the equations can be converted to a first order state space representation by letting y1=x and y2={dot over (x)}. The equations can then be represented as first order differential equations in the form {dot over (y)}i=Ayi+Bu and solved as a matrix with the force on the uppermost mass in the model being the hook load. In one implementation of the lumped mass model, the dynamic A matrix and input B matrix are discritized to get difference equations through an approximation as follows:
AD=[I+At+(A2t2)/2!+(A3t3)/3!+(A4t4)/4!+ . . . ]
BD=[It+(At2)/2!+(A2t3)/3!+(A3t4)/4!+ . . . ]B
For certain implementations, such as models with the masses 100 meters apart, the time sample may be t=0.01 seconds and the approximation may be truncated at the 4th power of t. The position and velocity of each mass can then be calculated recursively at every time step k+1 from the time step k data from the following equation:
Xk+1=ADXk+BDUk
Referring next to
Similar to the dynamic lumped mass model, in the dynamic lumped capacitance thermal model the wellbore is split into a plurality of axial sections such as that depicted in
In one implementation of the lumped capacitance model, once the wellbore environment is divided into sections, the sections are coupled together through the input and output of the fluid flow therethrough. In this approach, each section that is lumped together is assumed to have a constant temperature and between each section a resistance to heat transfer is modeled to represent the boundaries between the lumped capacitances, as best seen in
In operation, the system is designed to auto build the model for the particular well and is run in real-time, preferably starting when the service tool is close to a known location within the completion. Information such as well path including depth, azimuth and inclination, sea depth in offshore applications, tubing sizes, service tool geometry of each part including diameters and lengths, completion information for landing point locations, bottom hole temperature, surface temperature (rig floor and sea floor in offshore applications), properties of the fluid or fluids to be pumped or circulated, estimated frictional coefficients and the like are provided to the system. Once the system has this information, it builds the discrete model of the service tool string dynamics. The thermal model is also auto built and is rebuilt every time it is run to account for nonlinear changes of the model. In one implementation, the lumped mass model is run every 0.01 seconds with the lumped capacitance thermal model rebuilt and run every 50 iterations with the temperature changes included in the lumped mass model to calculate the thermal forces.
Once the subsurface model has been built, it may be used to optimize and reduce the risk associated with numerous completion operations and variables. In one implementation depicted in
In another implementation of the subsurface model as depicted in
In a further implementation of the subsurface model as depicted in
In yet another implementation of the subsurface model as depicted in
An additional implementation of the subsurface model is depicted in
Using the rate of change of adaptation of the model, the estimated error associated with the parameters of the model are determined, thereby providing a confidence level for the model. For example, following a treatment operation in a first zone, the service tool is reposition in a second zone. Due to the length of time for repositioning the service tool and the length of time between treatment operations, residual thermal effects may cause the service tool string to change in length. The present subsurface model will predict the length change but also predict the potential error in this calculation. In certain critical operations, this zone of confidence determination may indicate that service tool should be moved to a known landing point which will auto calibrate the system and provide improved confidence as to the position of the service tool relative the desired landing point.
Using the adaptive parametric controller associated with the lumped mass model, factors such as unloaded block movement are filtered out of the calculations. For example, if the hook load goes to an unloaded condition, indicating that the service tool string is being supported by the slips, and the block is relocated due to adding or removing a stand of pipe, the service tool position does not change. Accordingly, the system accounts for the various inputs, block movement with no hook load, to determine the no change in the service tool location should be included in the estimated service tool position.
As mentioned above, the subsurface model of the present invention may be coupled to a control system for operating the hook position and velocity as depicted in
While this invention has been described with reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. Various modifications and combinations of the illustrative embodiments as well as other embodiments of the invention, will be apparent to persons skilled in the art upon reference to the description. It is, therefore, intended that the appended claims encompass any such modifications or embodiments.
The present application is a United States National Stage commencement under 35 U.S.C. 371 of prior International Application no. PCT/US2009/066043, filed Nov. 30, 2009, which claims the benefit of the filing date of U.S. Provisional Patent Application No. 61/145,183, filed Jan. 16, 2009. The entire disclosures of these prior applications are incorporated herein by this reference.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/US2009/066043 | 11/30/2009 | WO | 00 | 9/10/2011 |
Publishing Document | Publishing Date | Country | Kind |
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WO2010/082975 | 7/22/2010 | WO | A |
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61145183 | Jan 2009 | US |