Abstract:
A reservoir production control system includes a plurality of wells for producing a reservoir linked to a central computer over a downhole communication network and a surface communication network. Both the downhole and the surface communication networks are wireless communications paths for transmitting downhole data and surface data to the central computer. Both networks include a series of interconnected tubing or pipe that allows transmission of data over electrically isolated portions of the pipe and tubing. After integrating and analyzing all relevant data and comparing the data with a reservoir model, the central computer initiates changes in a plurality of downhole control devices associated with the wells, thereby optimizing the production of the reservoir.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims the benefit of the following U.S. Provisional Applications under 35 U.S.C. 119(e), all of which are hereby incorporated by reference: 
   The current application shares some specification and figures with the following commonly owned and concurrently filed applications, all of which are hereby incorporated by reference: 
   The applications referenced in the tables above are referred to herein as the “Related Applications.” 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates in general to reservoir optimization and more specifically to petroleum wells having downhole independently addressable wireless measurement and control devices that communicate with surface power and telemetry devices such that production from individual zones within individual wells may be coordinated to optimize overall reservoir production. 
   2. Description of Related Art 
   Oil and gas reservoirs are extensive three-dimensional subsurface geological structures whose fluid contents are produced through arrays of wells which withdraw fluids from the reservoir only at points where the wells pass through the producing zones. As fluids are withdrawn at the wells, pressure differentials develop within the reservoir which in turn create displacement of fluids from more distant reservoir regions towards the producing wells. To assist in sweeping desired fluids towards the producing wells, it is common practice in some fields to pump water or other fluids into wells which are designated injection wells. 
   To assist in comprehending the changing condition of the reservoir and thus manage production from individual wells to optimize recovery from the field overall, it is common practice to develop a reservoir model which reflects the relevant characteristics of the formation&#39;s fixed matrix such as porosity and permeability, and the composition, pressure, and temperature of the fluids contained within that matrix. The parameters of both the matrix and the fluids are expected to change as fluids are withdrawn from the producing wells and injection fluids are introduced at the injection wells. Since the geological formations of the reservoir are generally heterogeneous, the starting values of the matrix and fluid parameters are spatial variables, and as production evolves the changes in these parameters are also spatially variable in addition to being time dependent. 
   The data used to generate a reservoir model come from many sources. Three-dimensional seismic surveys provide stratigraphy and faulting, and wireline logging, existing well production histories provide, and to a lesser extent seismic surveys, provide data on formation fluids. 
   The starting values of the reservoir model parameters adjacent to each well can be measured relatively easily using wireline logging tools before each well is cased, but once production has commenced the presence of the well casing prevents many of the measurements which can be made in an open hole. Even measurements which could be made through the casing are usually not performed in existing practice since doing so would require either removing the production hardware and tubing from the well and running cased hole wireline logs, or the use of permanent downhole sensors connected to surface equipment by cables which extend the full depth of the well. These cables are expensive, are not entirely reliable, often introduce operational problems, and their installation at the time of completion complicates that process. The same issue of requiring cables to operate downhole control equipment such as valves also discourages the use of such devices. When downhole control devices are absolutely required, the provision of permanently installed cables can be avoided by using slickline tools, but cost prevents these from altering the settings of downhole devices at frequent intervals. 
   All references cited herein are incorporated by reference to the maximum extent allowable by law. To the extent a reference may not be fully incorporated herein, it is incorporated by reference for background purposes and indicative of the knowledge of one of ordinary skill in the art. 
   BRIEF SUMMARY OF THE INVENTION 
   The difficulties inherent with restricted measurement and control are largely resolved by methods in accordance with the present invention. Wireless power and communications as described in the Related Applications enable the wells to provide real-time measurement of downhole conditions to update the reservoir model, and based on predictions made from the model, the well production is controlled to optimize field performance. The objective function for production optimization may be altered over time as product market conditions shift, production costs vary, or physical plant capabilities are changed. 
   The invention and development of wireless communication and electrical power transmission and control by means of pipes and tubing introduces the opportunity for widespread collection of oil field data, both (1) at the surface, through the network of facilities piping and injection and production distribution lines, and (2) in the subsurface, through well casing and tubing. The amounts and types of data that could be collected and the degree of control in remote parts of the units would provide a major advance in management of single wells, whole fields, or even company-wide assets. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  schematically illustrates a reservoir production control system according to the present invention being implemented on a company-wide basis to optimize the production of a plurality of reservoirs. 
       FIG. 2  depicts secondary production operations in a multi-layer reservoir being produced by two wells. 
       FIG. 3  illustrates primary production operations in a multi-layer reservoir by a production well, the production well experiencing water or gas breakthrough in one layer of the reservoir before another layer is oil depleted. 
       FIG. 4  is a flow diagram illustrating the measurement, modeling, and control actions method for closed-loop control of an individual well or a field. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring to  FIG. 1  in the drawings, a reservoir production control system  11  according to the present invention is illustrated. Reservoir production control system  11  is used to optimize the production of one or more reservoirs. A reservoir  13  includes a plurality of wells  15 ,  17 ,  19 ,  21  completed in the subsurface for producing oil and gas reserves from reservoir  13 . The exact number and type of wells present in a particular reservoir could vary significantly from reservoir to reservoir. In  FIG. 1 , well  15  is an injection well, well  17  is a conventional production well, well  19  is a multi-lateral production well, and well  21  is a data observation well. Each well includes a borehole that begins at a surface of the well and continues into a production zone within the reservoir. Preferably, the wells include casing that is cemented in the borehole during completion of the well. A tubing string or production tubing  29  is located in the borehole of each well. 
   Wireless data receptors or downhole data pods  31  are distributed in the boreholes of the wells. Downhole data pods  31  send and receive data along a downhole communication network  33 . Preferably, the downhole communication network allows transmission of data signals along an electrically isolated portion of the tubing string. In most cases, the electrically isolated portion of the tubing string is created between two ferromagnetic chokes placed on the tubing string. The transmission of data using such electrically isolated sections of pipe or tubing is described more fully in U.S. patent application Ser. No. 60/177,999, entitled “Toroidal Choke Inductor for Wireless Communication and Control,” filed Jan. 24, 2000, and U.S. patent application Ser. No. 60/178,000, entitled “Ferromagnetic Choke in Wellhead,” filed Jan. 24, 2000, which are both hereby incorporated by reference. Pods  31  may also be equipped to collect data about downhole physical characteristics of the well, including pressure, temperature, acoustic noise, seismic signals, resistivity, fluid turbidity, infrared response, flow rate in the pipe, vibration, or other measurements useful for monitoring the well. This data collection would be accomplished in the manner described in U.S. patent application Ser. No. 60/177,998, entitled “Petroleum Well Having Downhole Sensors, Communication, and Power,” filed Jan. 24, 2000, which is hereby incorporated by reference. Collected data would be transmitted to the surface of the well over the downhole communication network  33  using the methods described in U.S. patent application Ser. No. 60/177,999, entitled “Toroidal Choke Inductor for Wireless Communication and Control,” filed Jan. 24, 2000, and U.S. patent application Ser. No. 60/178,000, entitled “Ferromagnetic Choke in Wellhead,” filed Jan. 24, 2000. In some cases pod  31  would be equipped to operate accompanying downhole control devices  35 , which could include a submersible pump or a controllable gas-lift valve for modifying the flow rate of oil within the production tubing  29 . The downhole control device  35  could also include a chemical injector for injecting treatment chemicals such as corrosion inhibitors, scale inhibitor, foaming agents and paraffin solvents. The operation of downhole valves using the power transmission and communication techniques described above is more fully described in U.S. patent application Ser. No. 60/178,001, entitled “Controllable Gas-Lift Well and Valve,” filed Jan. 24, 2000, which is hereby incorporated by reference. Detection of failures of downhole equipment, such as gas-lift valve leakage, electric submersible pump vibration, and rod pump noise, would allow early remedial efforts that would improve productivity of the wells. 
   In addition to placement of wireless devices in the subsurface portions of the wells, a plurality of surface data pods  37  may be placed in a surface communication network  38  of interconnected pipes  39 . The interconnected pipes  39  are common in oil field operations and are generally used to fluidly connect the wells to tanks and separators  41 . Each of the interconnected pipes is also a potential data transmission path when a section of the pipes can be electrically isolated as described in U.S. patent application Ser. No. 60/177,999, entitled “Toroidal Choke Inductor for Wireless Communication and Control,” filed Jan. 24, 2000, and U.S. patent application Ser. No. 60/178,000, entitled “Ferromagnetic Choke in Wellhead,” filed Jan. 24, 2000. Preferably, the electrically isolated portions of the interconnected pipes are located between ferromagnetic chokes placed on the pipes. The wireless devices at the surface would interact with the subsurface devices to optimize well production in view of any operational constraints at the surface. These constraints might be (1) available gas for gas lift, (2) supply of water or other fluids for flooding projects, (3) upsets in production facilities such as oil/water separation, (4) emulsion control, and (5) other common occurrences encountered in manual operations. 
   Control of all of the operations described above resides in a central data collection computer  51 , which will have a reservoir model with which to compare the actual behavior of the reservoir being monitored by downhole data pods  31 . Reservoir conditions that change with time are often unattainable after wells have been completed and pipe cemented in place. With permanent pressure monitors available for timely pressure transient analyses, the progress of depletion of a reservoir can be closely monitored. Deviations from expected behavior, can be analyzed and in some cases, such as poor profile control, may be corrected by the downhole control devices  35 , or by well workovers. 
   Permanently installed resistivity monitors in producing wells would be effective in observing the effects of poor injection profiles. Referring to  FIG. 2  in the drawings, a multi-layer reservoir  61  with production well  63  and an injection well  65  is illustrated during flooding operations of secondary production. Downhole sensing and control devices are used to regulate injection into individual layers, in order to prevent early breakthrough of injected fluids and to minimize wasteful cycling of injectants during sweepout of the other layers. This is accomplished by monitoring and controlling flow rates at a number of locations along the injection interval. Alternatively, layers that flood out prematurely can be detected by salinity devices or other detectors spaced along the interval in production well  63 . 
   Referring to  FIG. 3  in the drawings, a multi-layer reservoir  71  being produced by a production well  73  is illustrated during primary production. Well  73  is experiencing water or gas breakthrough in one layer of the reservoir before another layer of the reservoir is depleted of oil. By placing downhole equipment and downhole control devices in the layers experiencing water or gas breakthrough, production from these layers can be excluded, thereby permitting continued oil production from layers that are relatively free of gas or water. 
   The values of downhole data are compared with the reservoir model prediction to determine if the reservoir is operating as expected. When the reservoir operating parameters diverge from expected behavior, new wells may be required, or wells may need to be shut in or abandoned; however, many corrective operations are potentially attainable with the proposed downhole control devices. 
     FIG. 4  illustrates a measurement and control sequence appropriate to such corrective actions. As illustrated in  FIG. 4 , such a sequence is cyclic:
         Measurements from downhole and surface sensors are collected and passed to the model;   The model may be updated from an external data source, for instance to alter desired production rate, and the measurements are compared to the model;   Based on the results of the comparison, decisions are taken on any action which may be required, and the model parameters are updated;   Any decisions for action are translated into commands which are transmitted to downhole actuators, and the cycle returns to the measurement step.       
   Reservoir management is not limited to optimization of a single field. Referring again to  FIG. 1 , a second central computer  77  and a third central computer  79  are associated with a second reservoir and a third reservoir, respectively. Similar to central computer  51 , the second and third central computers  77 ,  79  monitor downhole data and surface data over individual downhole communication networks (not shown) and individual surface communication networks (not shown). The data collected by second central computer  77  and third central computer  79  are integrated with that data collected by central computer  51  over a remote communication network  91 . The integration of data among the central computers  51 ,  77 ,  79  could include data for all of the fields operated by a particular company. This data can then be integrated and analyzed in conjunction with economic data  93  and world-wide economic trends, such as oil prices and supplies, national production controls, pipeline and tanker capacities, and location storage limitations. The overall effect of having large amounts of information and control in a central location by efficient wireless devices would allow effective optimization of production from all of a company&#39;s assets.