Patent Publication Number: US-8121790-B2

Title: Combining reservoir modeling with downhole sensors and inductive coupling

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application is a continuation-in-part of U.S. patent application Ser. No. 11/571,829, filed Nov. 27, 2007, which is a 371 of PCT Application No. PCTGB05/02110, filed May 27, 2005, (hereafter “the &#39;829 application”), which claims priority from GB Application No. 0416871.2, filed Jul. 29, 2004, which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to well characterization, and, more particularly, to characterization of a well using a series of measurements from sensors deployed along the sandface of that well to optimize a well model. Such a well may, for example, be a production well that can be exploited to produce oil and/or gas. 
     2. Description of the Prior Art 
     The following descriptions and examples are not admitted to be prior art by virtue of their inclusion in this section. 
     Substantial work has been undertaken by the oil and gas industry to obtain information that can be used to determine physical parameters that characterize wells. One such effort has resulted in monitoring equipment which can detect when problems occur during fluid extraction from a well and which warn an operator of an abnormal operating condition. Several types of monitoring equipment using various techniques for measuring physical parameters that characterize wells are known. For example, the temperature profile of a well is a physical parameter that can provide an operator with useful information to characterize the well. One technique to obtain a temperature profile employs a downhole optical fiber acting as a distributed temperature sensor. 
     A drawback to the use of monitoring equipment is that the equipment tends to provide an indication of the abnormal condition once the event has already occurred. This type of monitoring equipment only enables the operator to provide a reactive response to the abnormal operating condition and may not provide an accurate indication of exactly where in the well the cause of the abnormal condition lies. 
     In the &#39;829 application, a method is disclosed for characterizing a well using distributed temperature sensor data to optimize a well model. The method comprises the steps of providing a well model of thermal and flow properties of a well where the well model has a plurality of adjustable physical parameters. A data set made up of a plurality of distributed temperature sensor data profiles is provided where the profiles are taken at different times during the operation of the well. This method further comprises the step of running the well model with different combinations of the plurality of adjustable physical parameters to match the plurality of distributed temperature sensor data profiles. 
     It would be advantageous to provide a method of characterizing a well utilizing parameters other than downhole temperatures. This new and useful result is one of many stated and unstated results achieved by the method of the present invention. 
     SUMMARY OF THE INVENTION 
     In accordance with embodiments of the present invention, a method is provided for characterizing a well using a series of measurements deployed along the sandface of that well in order to optimize a well model. This method comprises the step of providing a well model with a plurality of adjustable physical parameters and providing a data set made up of a plurality of measurements along the sandface of a wellbore. A method according to an embodiment of the present invention further comprises the step of running the well model with different combinations of the plurality of adjustable physical parameters in order to match the plurality of sandface measurements. 
     In one embodiment of the present invention, the series of measurements may be distributed temperature measurements made along an optical fiber. In another embodiment of the present invention, the well may contain a communication device from the surface to the sandface and data regarding downhole parameters is transmitted to the surface by utilizing an inductive coupling technique. Such downhole parameters may, for example, include, but are not limited to, temperature, pressure, flow rate, fluid density, reservoir resistivity, oil/gas/water ratio, viscosity, carbon/oxygen ratio, acoustic parameters and chemicals sensing. In yet another embodiment of the present invention, the downhole measurements may be obtained by using a sensor string in combination with an optical fiber. 
     In another illustrative embodiment, a method according to aspects of the present invention may comprise the step of pre-processing the plurality of sandface measurements in order to make them consistent with one another. A method may, for example, but not limited to, include the pre-processing step of depth correction or of noise reduction. In other embodiments, a noise reduction step may advantageously be carried out by using a median filter. 
     In another illustrative embodiment, a method according to aspects of the present invention may comprise combining sensor data, downhole flow control devices and a surface modeling package. In such an embodiment, the flow control devices may be activated in a way so as to change the flow along the wellbore. That change may provide additional information that can be used to further increase the understanding of the reservoir. In the case of a multilateral well, for example, only one of the branches may be allowed to flow at any given time. By way of further example different chokes settings could be applied to change the flow distribution along a long horizontal well, and the settings of the flow control devices would be passed to the modeling device. 
     The measured data may also be used to further enhance the wellbore or reservoir modeling. For example, given a series of different flow rates in a wellbore, an optimal match between synthetic and measured data may only be possible through the use of a particular choice of friction along the wellbore. That value of friction may then be used in subsequent modeling runs. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Certain embodiments of the invention will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements. It should be understood, however, that the accompanying drawings illustrate only the various implementations described herein and are not meant to limit the scope of various technologies described herein. In the accompanying drawings: 
         FIG. 1  is a flow diagram that illustrates a method using distributed wellbore data to optimize a well model according to one embodiment of the present invention; 
         FIG. 2  is a pictorial diagram illustrating a system including communication apparatus and a sensor string for obtaining distributed wellbore data for use with a method in accordance with an embodiment of the present invention; 
         FIG. 3  is a pictorial drawing illustrating the combination of a sensor string and an optical fiber which are deployed downhole for obtaining distributed wellbore data for use with a method in accordance with an embodiment of the present invention; and 
         FIG. 4  is a flow diagram that illustrates using sandface sensor data to optimize a well model according to one embodiment of the present invention. 
     
    
    
     DESCRIPTION OF THE SPECIFIC EMBODIMENTS 
     It will be appreciated that the present invention may take many forms and embodiments. In the following description, some embodiments of the invention are described and numerous details are set forth to provide an understanding of the present invention. Those skilled in the art will appreciate, however, that the present invention may be practiced without those details and that numerous variations of and modifications from the described embodiments may be possible. The following description is thus intended to illustrate and not to limit the present invention. 
     As used here, the terms “up” and “down”; “upper” and “lower”; “upwardly” and “downwardly”; “below” and “above”; and other similar terms indicating relative positions above or below a given point or element may be used in connection with some implementations of various technologies described herein. However, when applied to equipment and methods for use in wells that are deviated or horizontal, or when applied to equipment and methods that when arranged in a well are in a deviated or horizontal orientation, such terms may refer to a left to right, right to left, or other relationships as appropriate. Additionally, the term “sandface” is utilized to refer to that part of the wellbore which penetrates through a hydrocarbon bearing zone. 
     Referring to  FIG. 1 , flow diagram  10  illustrates an embodiment of a method for characterizing a well using sandface sensor data in order to optimize a well model. The method comprises operating a well model  12  so as to model thermal and flow distributions in a well. The well may, for example, be a gas and/or oil producing well, such as that illustrated schematically in FIG. 16A of the &#39;829 application. The well model may be operated in either steady-state or transient conditions. In the first stage  12   a , the flow distribution in the well is modeled using a steady-state model. During the second stage  12   b , the thermal distribution in the well is modeled using a transient flow model. 
     The well model  12  may model the whole well, and not just a reservoir interval using a transient model. The well model  12  may perform a nodal pressure analysis to calculate fluid properties and use Joule-Thomson calculations to more accurately model temperature effects in the near well region. 
     In one embodiment, the information necessary to set-up the thermal and flow models is provided to a data processing apparatus by a user/operator via a GUI, such as that described in the &#39;829 application. The GUI may provide a sequence of data input screen images that the user can interact with in order to assign various values to various data fields. The GUI methodically guides the user through a data input process in order to obtain the necessary information. Use of such a GUI may simplify data entry and enable the user to apply an embodiment of a method of the invention without requiring detailed expert knowledge. 
     Once the thermal and flow distributions in the well have been modeled, sandface sensor data may be imported and conditioned, using the process at stage  14 . Data may be obtained at stage  14   a , for example, from real-time sandface sensor measurements and/or from one or more sandface sensor profiles that have already been acquired. One advantage of various embodiments of the present invention is that a plurality of sandface sensor profiles can be used to provide improved accuracy and to aid event prediction and parameter determination. Large amounts of historical sandface sensor data may be used in order to further improve the accuracy of the match between the sandface sensor profiles and the modeled thermal properties of the well. 
     The sandface sensor profile data may be pre-processed at stage  14   b  in order to make the sandface sensor profiles consistent with one another. The pre-processing may enable non-systematic noise variations, which may otherwise appear between the individual sandface sensor profiles, to be reduced. At stage  16 , the output of the well model  12  may be matched with the sandface sensor profiles. This matching may, for example, be done by minimizing the root-mean-square difference between the modeled and sandface sensor-derived traces. However, any of a number of numerical techniques may be employed which are well known in the field of data analysis for parameter determination. 
     If it is detected that the output of the well model  12  does not adequately match the sandface sensor profiles, the physical parameters of the well model  12  may be adjusted and the well model run again in order to provide a new model of the thermal and flow properties of the well. The process of matching, adjusting the physical parameters, and running of the model may continue in an iterative manner until a sufficiently accurate match between the sandface sensor profiles and the output of the well model  12  is obtained, or until it is determined that no satisfactory match can be found. 
     When a match is obtained, the results of the sandface sensor profiles and the modeled thermal and/or flow data can be provided to a user. The matched data may indicate to the user the location and magnitude of various physical parameters that characterize the well, and make it easier for the user to spot where any anomalies or unusual characteristics occur. Matched data can also be recorded, thereby enabling the monitoring of various physical parameters to be observed and compared over a period of time. 
     In one embodiment of the present invention, the sensor data may, for example, be obtained from a spoolable array of sensors such as those disclosed in U.S. Provisional Application No. 60/866,622 by Dinesh Patel, filed Nov. 21, 2006, which is also incorporated herein by reference. Such a spoolable array of sensors may be deployed along the sandface, and the sensors may transmit data to the earth&#39;s surface via an inductive coupling technique. Data respecting such, but not limited to, downhole parameters as temperature, pressure, flow rate, fluid density, reservoir resistivity, oil/gas/water ratio, viscosity, carbon/oxygen ratio, acoustic parameters and chemical sensing may be communicated to the earth&#39;s surface. 
     With reference now to  FIG. 2 , in yet another embodiment the sensor data from a sandface in wellbore  22  may also be obtained by using a spoolable array  20  comprising a plurality of addressable temperature sensors  21  that are deployed downhole and which may be addressed by communication apparatus  23  located at the earth&#39;s surface. When addressed, an addressable temperature sensor  21  may provide information respecting the individual temperature sensor&#39;s  21  identity and the temperature at the sensor&#39;s location downhole to the communication apparatus  23 . Such an array of spoolable temperature sensors is disclosed in U.S. patent application Ser. No. 11/767,908, by Pete Howard et al., filed Jun. 25, 2007 which is also incorporated herein by reference. 
     With reference now to  FIG. 3 , in a further embodiment of the present invention, the sensor data from a sandface in a wellbore may be obtained by simultaneously deploying a fiber-optic cable  31  and sensor cable  32  into the wellbore. The sensor cable  32  may, for example, comprise a plurality of temperature sensors  33  and a plurality of pressure sensors  34  that are disposed at spaced intervals along the sensor cable  32 . The spaced intervals for the pressure sensors  34  may, for example, be 20 meters. Distributed temperature sensor data may be obtained from fiber-optic cable  31  at one meter intervals, for example. 
     The sensor data obtained by sandface measurements may be preprocessed in a number of ways. For example, the sensor data received may include noise that must be reduced or otherwise removed. Such removal may, for example, be effected through the utilization of median and mean filters configured to remove spikes that may be present in the received sandface data. Such filtering techniques are well-known to those skilled in the art. 
     Yet another pre-processing step that may be required as one of depth control. Determination of the position of sensors deployed in the completion has been dependent upon surface measurements made as the completion is run into the ground. However, this measurement is sometimes incorrect. Even when correct, this surface measurement may not account for any compression or tension in the completion, potentially changing the length of the completion as it is deployed. In one embodiment of the present invention, sensors that are deployed downhole may be equipped with a small radioactive source. After deployment of the completion, a future run of wireline or coiled tubing can be made with a sensor configured to detect the presence of the radioactive source. The corrected depth of the sensor may then be established from the wireline or coiled tubing depth. Alternatively, radio frequency identification tags may be used, among other methods, and these tags may have an advantage of being coded with a serial number, etc. for further identification and confirmation of an individual sensor source position. 
     With reference now to  FIG. 4 , when a broader range of sensors beyond fiber optic cable is desired to be used, it may be necessary to use a more diverse modeling package then that described in  FIG. 1 . For example, rather than decoupling the flow properties in the wellbore from the thermal properties in the reservoir, as in an embodiment of the method illustrated in  FIG. 1 , a single modeling package such as wellbore flow model  22   a  may be used to model both properties. For example, one such package used to implement wellbore flow model  22   a  is the Eclipse program available from the Assignee of the present application. 
     Once the flow of distribution in the well has been modeled, sandface sensor data may be imported and conditioned using the process at stage  14 , with data obtained at stage  14   a  from real-time sandface sensor measurements and/or from one or more sandface sensor profiles that have already been acquired. The sandface sensor profile data may be pre-processed at stage  24   b  so as to make the profiles consistent with one another. The pre-processing may utilize any of the pre-processing techniques described above, in addition to other equivalent techniques. At stage  26 , the output of wellbore flow model  22   a  may be matched with the sandface sensor profiles. If it is determined that the output of wellbore flow model  22   a  does not adequately match the sandface sensor profiles, the physical parameters of the well model  22   a  may be adjusted and the well model run again to provide a new model of the flow properties of the well. 
     With reference still to  FIG. 4 , in one embodiment of a method of characterizing a well according to the present invention, a reservoir model  22   b  may be generated concerning the reservoir properties around the wellbore including but not limited to pressure, skin, permeability, and porosity. In this embodiment, the downhole sensors may provide information concerning the reservoir properties. Once the reservoir model has been constructed, the reservoir data from the sensors may be imported, pre-processed and matched against the output of reservoir model  22   b . If it is determined that the output of reservoir model  22   b  does not adequately match the reservoir profiles provided by the sensors, the parameters of the reservoir model  22   b  may be adjusted and the reservoir model run again. The process of matching, adjusting the physical parameters, and running the model may continue in an iterative manner until a sufficiently accurate match between the reservoir data from the sensors and the output of the reservoir model is obtained or until it is decided that no satisfactory match can be found. 
     While still referring to  FIG. 4 , an embodiment of a method according to the present invention may further comprise the step of establishing at least one control device  28  to change the flow characteristics of the production fluid in the well. Flow control device  28  may, for example, be set at the earth&#39;s surface and may comprise a choke, among other types of flow control devices. Alternatively, the flow control device  28  may be set in the wellbore with an active or adjustable flow control device. Active or adjustable flow control devices may be controlled through either well interventions such as with wireline or coil tubing or be interventionless and controlled automatically or through a well communication system. In the case of a multilateral well, for example, the flow control devices  28  may be set such that only one branch in the well is allowed to flow at any given time. By way of further example, different chokes settings could be applied to change the flow distribution along a long horizontal well. In such cases, the settings of the flow control devices  28  could be provided to the modeling device. 
     A method according to this embodiment may include the steps of providing a data set made up of a plurality of sandface measurements. In addition, a well model may be provided with a plurality of adjustable physical parameters. The method may further include running the well model with different combinations of the plurality of adjustable physical parameters in order to match the plurality of the sandface measurements. Thereafter, the setting of the flow control devices  28  may be changed resulting in the altering of the flow distribution of the production of the well. At which time, the steps of running the well model and comparing the well model results to the sandface data may be repeated and the process used to redefine the well model. 
     While the invention has been disclosed with respect to a limited number of embodiments, those skilled in the art, having the benefit of this disclosure, will appreciate numerous modifications and variations there from. It is intended that the appended claims cover such modifications and variations as fall within the true spirit and scope of the invention.