During the drilling and completion of oil and gas wells, it may be necessary to engage in ancillary operations, such as evaluating the production capabilities of formations intersected by the wellbore. For example, after a well or well interval has been drilled, zones of interest are often tested or sampled to determine various formation properties such as permeability, fluid type, fluid quality, formation temperature, formation pressure, bubblepoint and formation pressure gradient. These tests are performed in order to determine whether commercial exploitation of the intersected formations is viable and how to optimize production. The acquisition of accurate data from the wellbore is critical to the optimization of hydrocarbon wells. This wellbore data can be used to determine the location and quality of hydrocarbon reserves, whether the reserves can be produced through the wellbore, and for well control during drilling operations.
Downhole formation testing often involves a complex set of procedures to draw formation fluids into the formation tester and properly analyze the fluid sample. For example, a probe must be properly extended and engaged with the formation. Internal pistons and pumps must be properly adjusted and actuated to induce the proper fluid flow rate from the formation and into the formation tester. Pressure buildup times must be properly set to obtain the best possible test results. Formation testers also have operational limitations which must be considered in the testing control parameters. These are but some of the features of formation testing, and to perform a successful formation test requires a highly trained operator. Such training can be rare and costly, and inevitably includes manual error. Even with a highly trained and experienced operator, the numerous variables that are part of the formation testing process must be considered and managed. Failure to do so is common and leads to sub-optimal testing. The principles of the present disclosure overcome these and other limitations of the prior art.
For a detailed description of exemplary embodiments, reference will now be made to the accompanying drawings in which:
Appendix A includes Tables 1-4 and Graphs 1-7.
In the drawings and description that follow, like parts are typically marked throughout the specification and drawings with the same reference numerals. The drawing figures are not necessarily to scale. Certain features of the disclosure may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in the interest of clarity and conciseness. The present disclosure is susceptible to embodiments of different forms. Specific embodiments are described in detail and are shown in the drawings, with the understanding that the present disclosure is to be considered an exemplification of the principles of the disclosure, and is not intended to limit the disclosure to that illustrated and described herein. It is to be fully recognized that the different teachings of the embodiments discussed below may be employed separately or in any suitable combination to produce desired results.
In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . ”. Unless otherwise specified, any use of any form of the terms “connect”, “engage”, “couple”, “attach”, or any other term describing an interaction between elements is not meant to limit the interaction to direct interaction between the elements and may also include indirect interaction between the elements described. Reference to up or down will be made for purposes of description with “up”, “upper”, “upwardly” or “upstream” meaning toward the surface of the well and with “down”, “lower”, “downwardly” or “downstream” meaning toward the terminal end of the well, regardless of the well bore orientation. In addition, in the discussion and claims that follow, it may be sometimes stated that certain components or elements are in fluid communication. By this it is meant that the components are constructed and interrelated such that a fluid could be communicated between them, as via a passageway, tube, or conduit. Also, the designation “MWD” or “LWD” are used to mean all generic measurement while drilling or logging while drilling apparatus and systems. The various characteristics mentioned above, as well as other features and characteristics described in more detail below, will be readily apparent to those skilled in the art upon reading the following detailed description of the embodiments, and by referring to the accompanying drawings.
Referring initially to
In some embodiments, and with reference to
Referring to
The formation tester 120 may include a plurality of transducers 115 disposed on the formation tester 120 to relay downhole information to the operator at surface or to a remote site. The transducers 115 may include any conventional source/sensor (e.g., pressure, temperature, gravity, etc.) to provide the operator with formation and/or borehole parameters, as well as diagnostics or position indication relating to the tool. The telemetry network 100 may combine multiple signal conveyance formats (e.g., mud pulse, fiber-optics, acoustic, EM hops, etc.). It will also be appreciated that software/firmware may be configured into the formation tester 120 and/or the network 100 (e.g., at surface, downhole, in combination, and/or remotely via wireless links tied to the network).
Referring briefly to
Referring next to
The piston assembly 208 includes a piston chamber 252 containing a piston 254 and a manifold 256 including various fluid and electrical conduits and control devices. The piston assembly 208, the probe 220, the sensor 206 (e.g., a pressure gauge) and the valve assembly 212 communicate with each other and various other components of the probe collar 200, such as the manifold 244 and hydraulic system 242, as well as the tool 10 via conduits 224a, 224b, 224c and 224d. The conduits 224a, 224b, 224c, 224d include various fluid flow lines and electrical conduits for operation of the probe assembly 210 and probe collar 200.
Referring now to
In
Formation testing using the various formation testers described above, as well as other similar formation testers known in the industry, requires highly trained operators to manually set formation testing parameters and controls in an attempt to obtain the best results possible. For example, a skilled operator must set appropriate flow rates and buildup times for the components of the formation testers described herein such that the formation fluids can be properly measured for useable results. As will be described below, the principles of the present disclosure are embodied in various methods and systems for optimizing the testing mode, parameters, and controls for a formation tester. In some embodiments, the method is partially optimized by automating the testing mode and procedure and the adjustability of the parameters and controls. In some embodiments, the testing modes for the single and dual probe formation testers 300, 400 of
In some embodiments, an automated and optimized formation testing method includes controlling the testing procedure based on multiple criteria and parameters as will be further detailed below. In some embodiments, the method is based on a set of test criteria and/or control parameters used to target a test objective. In further embodiments, a set of formation tester tool parameters or specifications based on the operating range and limitations of the formation tester supplements the method. For purposes of the following description, the formation testers of
Upon a first drawdown using the drawdown piston 208 and the corresponding probe assembly 210 of
In some further embodiments, a control parameter as well as a test criterion are established prior to a first formation test. Referring now to
In some embodiments, the collecting 610 and adjusting 612 steps, as well as the determining 506 and the performing 508 steps, occur while downhole. In certain embodiments, the collecting 610 and adjusting 612 steps occur in close temporal proximity, such that they occur during the same trip into the well bore or during the same formation testing run or sequence. Similarly, the determining 506 and the performing 508 steps occur in close temporal proximity such that the resulting formation tests can be optimized during a single trip or testing sequence. In some embodiments, the noted methods include automatically executing the optimized formation test while downhole.
Referring next to
In some embodiments, the previously described methods can be used to optimize testing for a formation tester with multiple probes. For example, for the dual probe formation tester 400 of
The control parameters described above are input parameters including test control objectives, formation tester specifications, or combinations thereof In some embodiments, the control parameter is a test flow rate or initial drawdown rate, or a drawdown volume. In further embodiments, the control parameters may include those parameters listed in Table 1 appended to this disclosure. Table 1 includes control parameters that are specified by the engineer or the client or customer, for example. In some embodiments, the parameters can be stored in the formation testing tool, while in other embodiments parameters can be selected for downloading while testing. With reference to Table 1, the listed control parameters are exemplary control parameters that may be used, adjusted, and optimized in the various embodiments disclosed herein. For example, each drawdown pressure can be controlled to a minimum pressure. Previously obtained drawdown/buildup data can be used to optimize the next drawdown/buildup. In some embodiments, a maximum pretest volume that is available is used. In some embodiments, a desired drawdown pressure and time is maintained during testing. In other embodiments, a buildup time is limited based on pressure stability, or a buildup time is limited to no less than a minimum specified or predetermined buildup time. In further embodiments, a buildup time is limited to no greater than a maximum specified or predetermined buildup time.
In some embodiments, when a variable rate control is selected (see Table 1), the initial rate is increased or decreased during the test to maintain a drawdown control pressure. If the formation tester tool parameters do not allow for variable rate control, other control parameters can be used such as a minimum control drawdown pressure to cause the drawdown to terminate. In some embodiments, the primary parameters that are adjusted and or optimized after a formation test include initial drawdown rate, drawdown volume, and minimum drawdown pressure (see Table 1).
The embodiments herein also incorporate or take into account formation tester tool parameters or specifications. With reference to Table 2, appended, exemplary tool parameters include probe size, number of probes, flow rate control range (maximum and minimum), total pretest volume available, minimum control volume, drawdown pressure limits (maximum and minimum), flowline volume, system response time and maximum number of drawdowns possible. However, the listed parameters are not limiting and other exemplary control parameters are provided and contemplated throughout this disclosure. Further, these parameters and their associated objectives can change based on various factors. For example, normally it is desirable to use the maximum pretest volume; however, if the objective is to minimize total testing time, then a large volume is not helpful. Thus, the method and it's optimization algorithms would need to be revised for this alternative objective. In some embodiments, a maximum volume is chosen because it is normally assumed that the best test results are obtained when moving the largest volume of formation fluids as possible from the formation.
In some embodiments, the formation tester parameters or specifications are stored in downhole memory, as described with reference to
Referring now to Table 3, appended, the embodiments here include test criteria. The test criteria are listed in Table 3, and include maximum drawdown rate, drawdown differential desired, drawdown limit (bubble point), buildup pressure stability, buildup temperature stability, and stability time period. As illustrated by Tables 1-3, some embodiments herein include a control parameter that is a characteristic or value of the formation test or tool that can be directly controlled, while a test criterion is a passive baseline, limit, or boundary that can be used to trigger an action or step in the formation testing process when met.
In certain embodiments, before control parameters can be adjusted and optimized, calculations must be made based on the information gathered and the known control parameters and test criteria. Referring to Table 4, appended, a list of optimization calculation variables is provided, as will be described in more detail below. In some embodiments, controlling each drawdown pressure to a minimum pressure is a significant objective, particularly for the first pretest drawdown. If the first pretest drawdown cannot be controlled above a pressure cutoff point, then any subsequent test optimization may not be possible using traditional drawdown/buildup testing methods. However, controlling to a minimum pressure, in some embodiments, allows calculations to be performed resulting in test adjustment and/or optimization, as will be described below.
In exemplary embodiments, a method for formation testing includes establishing a set of control parameters for testing a formation, performing a first formation test using the testing control parameters, determining optimum control parameters for a next formation test based on results from the previous formation test, performing the next formation test using the optimum control parameters, and then repeating the determining optimum control parameters and performing the next formation test for each subsequent formation test. In further exemplary embodiments, a method for formation testing includes establishing a control parameter and a test criterion for testing a formation, providing a formation tester equipped with the control parameter and the test criterion in a well bore at a test location, performing a first formation test, controlling the first formation test using the control parameter and the test criterion, collecting test data from the first formation test, and adjusting the control parameter using the test data.
In certain embodiments described herein, pressure tests are referred to when describing the methods and processes that exemplify the disclosure. However, it is understood that formation tests other than pressure tests are contemplated. As described, the testing control parameters may include formation tester specifications. In some embodiments, the control parameters may be associated with test control objectives. In some embodiments, the testing control parameter includes test control objectives including at least one parameter that controls a formation test in progress and formation test initial parameters. The formation test initial parameters may include at least one of a flow rate, a drawdown volume, a drawdown time, and a buildup time range. In other embodiments, the test control objectives include controlling each drawdown pressure of the formation tests to a minimum pressure. In still other embodiments, the test control objectives include controlling each drawdown of the formation tests using a predetermined range of flow rates. In certain embodiments, the test control objectives include controlling each drawdown of the formation tests to a maximum drawdown time. In some embodiments, the test control objectives include controlling each buildup of the formation tests to a minimum buildup time. In some embodiments, the test control objectives include controlling each buildup of the formation tests to a maximum buildup time. In further embodiments, the method includes controlling a buildup time based on an objective to terminate the buildup before the maximum buildup time is reached, and wherein the objective can be supplemented with test criteria including a pressure stability, a temperature stability, or a combination thereof. As used in some embodiments herein, a control parameter is a characteristic or value of the formation test or tool that can be directly controlled, while a test criteria is a passive baseline, limit, or boundary that can be used to trigger an action or step in the formation testing process when met.
In some embodiments, the method includes moving a drawdown device to flow a formation fluid at a flow rate into the formation tester for a pretest, thereby producing a drawdown pressure, and automatically controlling the drawdown pressure to a minimum pressure criterion Pmin by controlling the flow rate or terminating the drawdown device movement. The method may include a minimum pressure Pmin that is determined by an absolute pressure limit determined using a hydrostatic well bore pressure and tool specification, wherein the absolute pressure limit defines the lowest pressure the formation tester can reduce a pressure from the hydrostatic well bore pressure when performing a drawdown. The method may include terminating the pretest drawdown substantially at the minimum pressure Pmin. Further, the tool specification includes a system response time Δtsys, and the method further includes predicting a pressure within the system response time Δtsys and, when the predicted pressure at Δtsys is at or below the minimum pressure Pmin, then terminating the pretest drawdown. Also, the predicting step and the step of terminating when the predicted pressure at Δtsys is at or below the minimum pressure Pmin further includes performing a regression of recorded drawdown pressure data using a predictive function which estimates when the minimum pressure Pmin will occur.
In some embodiments, one or more of the formation tests includes controlling a buildup time of a pretest. In some embodiments, the buildup time is controlled by not terminating the buildup until at least a minimum buildup time has passed. In some embodiments, the buildup time is controlled by terminating the buildup when the change in pressure or temperature over a time range meets the control parameter or the test criteria. In some embodiments, the buildup time is controlled by terminating the buildup when a predetermined maximum buildup time has been reached.
In some embodiments, the method includes, after the initial drawdown and pretest, determining an optimized drawdown rate qdo and a volume. The method may include determining estimated formation parameters from the initial pretest. Then, an optimal drawdown pressure differential ΔPdo is determined based on the previous pretest, test control objectives of Table 1, and formation tester specifications of Table 2. Further, the method includes calculating an initial estimate of the optimized drawdown rate qdo using the estimated formation parameters determined from the initial pretest, the optimal drawdown pressure differential ΔPdo based on the previous pretest, the test control objectives of Table 1, and the formation tester specifications of Table 2. Next, it is determined whether the optimized drawdown rate qdo, a drawdown time tdo, and a volume Vdo are within predetermined limits. In some embodiments, the optimized drawdown rate qdo includes:
formation parameters from the preceding drawdown including (see also Graph 1 of Appendix A):
an optimal drawdown pressure estimate including (see also Graph 2 of Appendix A):
an optimal drawdown rate estimate including (see also Graphs 3-7 of Appendix A):
adjusting the optimal drawdown rate to be within the formation tester limits, including:
adjusting the drawdown time and the drawdown volume to practical limits, including:
In some embodiments, the pretest is continued for at least a specified minimum buildup time tbu
In some embodiments, the method includes signal pulsing the buildup stability σbu to the surface of a well. In some embodiments, the method includes indicating supercharging with a negative value of the buildup stability σbu and changing a testing procedure in response to the negative buildup stability σbu. In other embodiments, the method includes indicating that a mudcake thickness has substantially stabilized if the buildup stability σbu indicates a pressure is increasing, and estimating a supercharge pressure using a stable mudcake model. In still other embodiments, the method includes indicating that a mudcake thickness is increasing or unstable if the buildup stability σbu is negative or a pressure is decreasing, and estimating a supercharge pressure using a dynamic mudcake model.
In some embodiments, the method includes maintaining a drawdown pressure differential ΔPdo during the second or subsequent formation test.
In some embodiments, the control parameter comprises the test control parameters of Table 1 and the formation tester tool parameters of Table 2.
In some embodiments, the control parameter is stored in a formation tester memory, downloaded while testing, or a combination thereof The method may include automatically executing the adjusting and using steps of the method disclosed herein while downhole. Further, the optimized formation test may be executed automatically while downhole. The methods described herein can be used as an advisor to the formation tester operator or implemented with the formation tester for fully automated testing. For formation testing while drilling tools (FTWD), for example, downhole implementation of the testing and optimization methods described herein provide benefits due to limited communication with the formation tester while downhole. Using the methods described the formation tester can adapt to conditions with no intervention by an operator. All of the methods, processes, and logic can be implemented within the real-time control software without requiring the operator to directly communicate with the formation tester. This enables a formation tester to work autonomously and achieve the test objectives.
In some embodiments, an adjusted value of the test criteria set comprises a bubble point drawdown limit Pbp (Table 3).
In some embodiments, the method includes storing the control parameter and/or the test criterion in a testing database, and documenting at least one of the formation tests in the testing database.
The embodiments set forth herein are merely illustrative and do not limit the scope of the disclosure or the details therein. It will be appreciated that many other modifications and improvements to the disclosure herein may be made without departing from the scope of the disclosure or the inventive concepts herein disclosed. Because many varying and different embodiments may be made within the scope of the inventive concept herein taught, including equivalent structures or materials hereafter thought of, and because many modifications may be made in the embodiments herein detailed in accordance with the descriptive requirements of the law, it is to be understood that the details herein are to be interpreted as illustrative and not in a limiting sense.
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/US12/25820 | 2/20/2012 | WO | 00 | 8/20/2014 |