In developing most deepwater fields with limited number of wells, intelligent well systems which consist of many valves and sensors are employed to maximize production capacity under facility constraints. Analysis of sensor data unaffected by wellbore effects allows operators to estimate key reservoir parameters, well capacity and calculate actual flow rates at zonal level. Decisions for operational control is made based on data analysis, the result of which is used to optimize overall field performance and maximize return on investment.
Understanding pressure sensors placement issue is important from pressure-transient analyses viewpoint. Pressure gauges should ideally be placed as close to the perforations as possible to ensure the pressure data is unaffected by friction in the tubing between the perforations and pressure gauges but placement of the gauge is dictated by completion hardware configuration and can be located far away from the point of reservoir fluid entry. This may result to potentially erroneous measured pressure data and may lead to the calculation of inaccurate reservoir parameters and an overestimated mechanical skin value from pressure buildup response.
One of the main operating constraints in deepwater wells is flux limit which is a practical well surveillance tool used to monitor and operate sand control completions, maintaining each producing interval at a maximum safe operating rate, and also monitoring well impairment to allow for proactive remedial operations. Since the flux limit is a function of mechanical skin, if the mechanical skin is over estimated because frictional losses are not properly accounted for, well production may be unnecessarily constrained.
In this paper, analysis was done using a wellbore/reservoir simulator to account for frictional effects in the tubing between the perforations, and the gauge for a field example. Sensitivity analysis was also carried out at different flow rates for each well and simple correlations were developed for predicting frictional effects. Results obtained from calculations showed that pressure gauges placement effect is significant as flow rate and gauge distance from perforations increases. Correcting for this effect increased the flux limit thus increasing production rate on several wells that were previously flux constrained.