In 1999, an oilfield experiment was initiated to test the application of electrical measurement technologies to permanent reservoir monitoring. The principal objective of the experiment was to demonstrate the feasibility of monitoring water movement between an injection and an observation well. This paper describes the interpretation of the data provided by the resistivity arrays and discusses the data quality and reliability of the measurements.Two wells were drilled into the Mansfield sandstone reservoir in Indiana, U.S.A. The D-8 injector well was located in the center of four development wells. The OB-1 monitoring well was offset 233 ft to the southwest in a location midway between the D-8 injector and the No. 3 production well. The injector was instrumented with a 16-electrode resistivity array that was run on the outside of insulated casing and cemented into the annulus of the well. A similar array was cemented into the annulus of the monitoring well.In March 1999, the D-8 well was perforated and acidized. A surface gauge was used to monitor injection rates and pressures. Initially, injection proceeded at a rate of approximately 20 B/D, increasing to 90 B/D after fracture stimulation. The D-8 array records responses to wellbore operations and injection. It clearly distinguishes the movement of the waterfront in different zones. The OB-1 electrical array clearly indicates early water breakthrough by means of an induced fracture. The data show good signal-to-noise ratio and high reciprocity.The experiment has demonstrated the viability of using permanently installed resistivity arrays to monitor the movement of oil/ water contacts and salinity fronts that are some tens of feet away from the wellbore. Results demonstrate the feasibility of using such arrays to monitor oil/water contact movements remote from injection, monitoring, and production wells.
In 1999 an oilfield experiment was initiated to test the application of electrical measurement technologies to permanent reservoir monitoring. The principal objective of the experiment was to demonstrate the feasibility of monitoring water movement between an injection and observation well. This paper describes the utility of the data provided by the resistivity arrays and discusses data quality and reliability of the measurements. Two wells were drilled into the Mansfield sandstone reservoir in Indiana. The D-8 injector well was located in the center of four development wells. The OB-1 monitoring well was offset 233 ft to the southwest in a location midway between the D-8 injector and the No. 3 production well. The injector was instrumented with a 16-electrode resistivity array that was run on the outside of insulated casing and cemented into the annulus of the well. A similar array was cemented into the annulus of the monitoring well. In March, the D-8 well was perforated and acidized. A surface gauge was used to monitor injection rates and pressures. Initially, injection proceeded at a rate of about 20 B/D, increasing to 100 B/D after fracture stimulation. The D-8 array records responses to perforation, acidization, swabbing, fracturing, and injection. It clearly distinguishes the movement of the waterfront in different zones. The data show good signal-to-noise ratio and high reciprocity. The OB-1 electrical array clearly indicates early water breakthrough via an induced fracture. The arrays show no degradation of signal over the 17-month duration of the experiment. The experiment has demonstrated the viability of using permanently installed resistivity arrays to monitor movement of oil-water contacts that are some tens of feet away from the wellbore. Results demonstrate the feasibility of using such arrays to monitor oil-water contact movements remote from injection, monitoring, and production wells. Introduction The industry drive toward using intelligent wells to improve recovery efficiency will require continuous monitoring and optimization of reservoir drainage. Currently, commercial monitoring is through sensors that measure flow in the wellbore and permanent borehole pressure gauges. These sensors allow for reactive reservoir management: opening or closing production zones as a response to breakthrough of unwanted fluids into the wellbore. Proactive reservoir management is possible if we are able to detect the advance of unwanted fluids in the formation, prior to their breakthrough into the production stream. We have conducted an oilfield experiment to demonstrate that sensors can be deployed and used to monitor fluid movement remote from the wellbore.1 As this was the primary objective of the experiment, emphasis was placed on demonstrating the feasibility and utility of such measurements, rather than on testing a commercially viable deployment scheme.
We have tested new technologies for real-time monitoring and control of water influx to horizontal wells with sand control completions. We drilled a horizontal well in a thin oil column in Indiana, which was completed openhole with sand screens and a gravel pack. External casing packers subdivide the annulus into three zones. An electrical valve, which also records the annular and tubing pressure, controls inflow to each zone. Twenty-one centralizers act as electrodes to form a resistivity array that spans the 694-ft-long completion. The well is also equipped with a fiber-optic-distributed temperature sensing system. The well has been produced since November 2001 and provides real-time data that are shared across a geographically distributed network and used to optimize the production of oil from the well. The data from the pressure sensors and the resistivity array have been jointly interpreted to dynamically update the static reservoir model, which was initially based on observations in offset vertical wells. The pressures recorded from the three electrical valves provide high-frequency data to characterize the near-well heterogeneity of the formation. This is critical to computing an optimum production strategy. Zonal well tests, combined with interference testing between zones and wells, allow for estimation of communication between zones and the productivity index of each zone. The resistivity data enable detection of water saturation changes both in the formation and in the wellbore. The completion technology tested in this well offers the potential to intelligently operate long horizontal sand control completions by combining real-time monitoring with downhole inflow control. Introduction The production performance and ultimate recovery of horizontal wells are often less than predicted by fluid flow simulations. Premature breakthrough of water or gas to the wellbore, caused by uneven influx along the well, is one reason for this disappointing performance. We tested a variety of sensing technologies that facilitate the intelligent operation of remotely operated valves to maximize well productivity and ultimate recovery of oil. To achieve this test, we installed a completion in a very thin (originally 13-ft thick) oil column in the East Mount Vernon Unit of the Lamott Consolidated Field, Posey County, Indiana (Fig. 1). This unit is operated by Team Energy and produces oil from the Tar Springs and Cypress sandstones. Most production is from the Mississippian Cypress sandstone reservoir. The previously existing vertical wells produce at a very high water cut (approximately 95%) because of the thin nature of the Cypress reservoir oil column.
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