Abstract
In August 2009, ISO Sand Screen Standard 17824 was approved for use. Subsequent qualification testing for burst and collapse resistance of wire wrap screens(WWS) by the service companies (SC) indicated there were inconsistent test results with using the formulated pill required by the new standard. In early 2011, revision 1 to 17824 was initiated to address this problem.
For deepwater completions, a high strength sand screen is often necessary to withstand the pressures when a FLC pill is applied to seal the well. The FLC pill needs to be a special formulation to insure the bridging agents can seal at applied burst pressures exceeding 2500 psi.
A service company reported that there were significant changes in the percentages of over, near, and under size of FLC pill residue taken from tested screens. The oversize material had been reduced by 35%, and the near size had been reduced about 20%. This indicated the bridging agents in the pill may be too weak to bridge properly at elevated pressures. Four different bridging agents, consisting of fifteen different formulations, were evaluated for crush resistance, subjected to different lab tests to evaluate their ability to seal the screen effectively with minimal leak off, and to maintain this seal at high applied pressures. Tests were done to verify the pill can be lifted off the screen with minimal pressure. It is planned that the two most promising formulations will then be subjected to full scale collapse and burst testing to verify that the high strength FLC pill will provide consistent test results for wire wrap screens.
The goal of the modified FLC pill formulation is that the FLC pill remains stable and provides an effective seal until the applied pressure results in sufficient changes in the dimensions and slot of the WWS causing loss of sand control. Ideally, the burst and collapse resistance should approach the mechanical failure of the wire wrap screen being used. The FLC pill needs a different formulation to insure the bridging agents can also seal at applied burst pressures exceeding 2500 psi. Several successful completions have been reported using a special FLC pill with a very heavy wire wrap screen design. The results of the improved FLC pill testing will likely have an impact on wire wrap screen ratings for deep water completions.
