Startup of Screenless Sand Control Through Coiled Tubing Fracturing in Shallow Unconsolidated Reservoir
Authors: Lee W.K. , Zemlak W. , Qian X. 
Published: December 2007

This paper describes the startup and application of coiled tubing- (CT-) conveyed fracturing for sand-control purposes in an oil field in Indonesia. Sand production becomes a major problem where well servicing is routinely performed to replace worn or stuck subsurface artificial lifting equipment. Some of the producer wells are slimhole, which prevents the use of conventional sand control using screen and gravel because it restricts the production flow severely. A recent field test was performed in four wells by fracturing through CT to provide screenless completion. The ultimate goal was to achieve an acceptable sand control in these weak formations while restoring production. We demonstrate that not only did the treatments achieve the objective but they also stimulated the well and improved well management.

Introduction

This oil field has principal oil-bearing sands of Miocene age with combined pay thickness averaging 140 ft and ranging in depth from 430 to 700 ft. The sands are unconsolidated and highly permeable. Tertiary recovery method is being used to enhance the oil recovery to about 60% of original oil in place.

In some thermally mature sections of the field, steam injection activities are ramped down as heat requirements are becoming lower. The situation allows injectors and temperature-observation wells to be recompleted into producers. These wells were initially completed as monobores, with 4-, 7-, or 9 5/8-in. nominal outside diameter (OD) casing. No sand-control completion was installed in most wells during recompletion, because of concerns on production and restricted wellbore access associated with conventional sand-control completion with screens. The typical perforation scheme is 0° phasing, 1- to 2- shots per foot (spf) perforation density, 9- to 30-ft interval length, and 0.4-in. hole entrance. Fig. 1 presents the completion for this type of well.

Some wells produced as much oil as in active areas, and others produced at a marginal rate, as expected. However, severe sand production was inevitable, leading to frequent well servicing and lost oil production. This triggered the concept of screenless sand control (SSC), which was introduced end of 1999. The concept was to perform tip screenout (TSO) fracturing with curable resin sand (CRS) as the proppant in an oriented-perforated well. After placement, the proppant will form a stable sand filter media in the perforation tunnels and around the near-wellbore area to stop formation sand production, and CRS will prevent proppant flowback. CT fracturing technique was selected for its efficiency for shallow-multizones formation fracturing and pin-point placement of the proppant.

The idea of using CRS is not new in the application of sand control worldwide.1 In the past, single-stage TSO fracturing was employed to place the proppant into the formation over a typical gross pay length of between 50 and 100 ft for SSC. However, the technique failed to achieve acceptable sand control becausethe length of the perforated interval was too large to control placementnot all perforations received CRS during placementformation sand bridged over some of the perforations