Fracturing, Frac-Packing and Formation Failure Control: Can Screenless Completions Prevent Sand Production?
Authors: Morita Nobuo , Burton Bob , Davis Eric 
Published: December 2007

Some successful results have been reported for screenless frac-packing methods, however, no scientific guidelines are given on the conditions under which a screen can be eliminated from a well. This paper collects field data from sand producing wells and reviews the onset and the rate of sand production for those wells with and without hydraulic fractures. From these field observations and numerical modelling analysis, guidelines are established for when a screen must be run and when a screen can be eliminated.

Introduction

If reliable sand control can be established by fracturing a well without resorting to frac-packing around a screen, a significant economic gain can be attained. This economic gain occurs due to improved operational simplicity (rig time and workover/completion cost are reduced by eliminating the screen) and through improved well productivity (production rate is not reduced due to screen plugging or gravel pack plugging).

Some successful sand control applications have been reported for screenless, fracture only, methods, however, the minority of wells are still completed as combinations of fracturing and gravelpacking (ie: frac&packs/frac-packs). This industry conservatism is based on a number of cases where sand problems have occurred after performing fracture treatments without a screen.

Analysis of these field results indicates that there are some special conditions which allow successful sand control using screenless fracturing while under the majority of conditions, a frac & pack around a screen is required.

Operational decisions regarding whether or not to run a screen are usually based on one of two opposing views which currently hold sway within the oil industry:a screen can be eliminated if the fracture provides sufficient drawdown reduction to stay below an estimated sand flow threshold/tensile failure limit; ora screen must be used when depletion will occur over the life of the well such that shear failure of the formation will occur.

This paper reviews sand production data on a number of fields with and without hydraulically fractured wells and compares the onset of sand production for fractured wells to the general population in order to assess the benefits of fracturing in controlling sand production. From numerical analysis of these field cases, guidelines are developed for determining when a screen is needed to control sand in a fractured well. The data shows that although a hydraulic fracture may delay the onset of sand production by reducing drawdown, sand production can still occur due to reservoir pressure depletion induced shear failure. Alternatively, the onset of sand production due to reservoir pressure depletion is usually seen to be delayed and/or eliminated when a fracture is created from a strong zone. Field experience also shows that sand production rates are often smaller for fractured wells than for unfractured wells as reservoir pressures and flow rates decline.

This paper includes (1) guidelines for determining when a screen is needed to control sand production from fractured wells and (2) methods to eliminate sand control screens for fractured wells under special field conditions. The paper tries to provide information to help solve the controversial issue of whether to use or eliminate sand control screens in fractured wells.

Field Observations and Theory:

Field conditions, numerical model input data, and field observations The technique used in this work is to observe and analyze data from fields which have sufficient history to allow a comparison of the onset and rate of sand production during reservoir life. From numerical analysis of these field cases, guidelines are derived on when a screen is required to effectively control sand production in fractured wells. Field data from a number of oil and gas reservoirs are used in the work. These oil and gas reservoirs are located in a number of sedimentary basins around the world and cover a range of reservoir and rock properties.

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