Novel Filter Cake Breaker Design and Successful Use for OHGP Carrier Fluid

Abstract

The Serrette and Savonette gas fields offshore Trinidad will be developed through use of open hole gravel pack (OHGP) completions. This completion type was chosen as the preferred completion technique for sand control for these fields. Due to a wide range of expected fluids densities required, the fluids design considered both monovalent and divalent brine as the base fluid for water-based reservoir drill-in fluid (RDF), completion brine and gravel pack carrier fluid (GPCF). Low pore pressures in the field did not allow applying high drawdowns during backflow of the wells, therefore chemical breaker technology was recommended by the Operator to be included in the fluids package to assist with filter cake removal and wells clean-up. The large pore throats of the formation necessitated the use of a high concentration of coarse sized particles in the RDF for bridging which caused a considerable decrease in retained permeability and potentially plugging of gravel and screen from assurance laboratory testing. High overbalances used during drilling potentially would exascerbate any near wellbore damage from the use of water based fluids.Most of the commercially available filter cake breakers are compatible only with monovalent brines and the acid precursors in use could not guarantee the low corrosion requirements required, nor result in ideal rheological properties expected from the GPCF over time since Hydroxy-ethyl-cellulose (HEC) was selected as the viscosifier to transport and deposit the gravel.GPCF with incorporated breaker, composed of a novel chelant compatible with divalent brines and a buffer, was chosen as a solution for the Serrette project. The system was modified for successful use on the Savonette Field. Screening tests were performed by the supplier to obtain an optimized formulation that would satisfy GPCF requirements and logistics. The final formulations were tested and approved at the operator's fluids laboratory. Several wells have been completed using the procedure and products. All have achieved outstanding production rates. The flow initiation pressures measured during wells start-up were noted to be less than those historically seen in the field.The GPCF with incorporated breaker is believed to have assisted with filter cake removal and well clean-up and also contributed to the fact that the gas requirements from the project have been met. The paper will focus on the development of fluids package for successful implementation in the field to deliver the wells and planned gas production.