Active Filter-Cake Technology – Eliminating the Need for Post-Completion Cleanup

Abstract

A new generation Reservoir Drill-in Fluid (RDF) has been developed to mitigate the potential of damage to the producing formation and eliminate the need for post-completion cleanup.This RDF system was developed to perform synergistically where openhole gravel-packing or expandable screen completion styles are utilized. This new RDF system generates an active filter cake which is impermeable to aqueous fluids, thus reducing fluid loss into the producing formation. Concurrently, the now residual filter cake is permeable to formation hydrocarbons. This system utilizes organophilic components which generate preferential oil channels in the residual filter cake, thereby, eliminating the need for stimulation/cleanup from either internal or external chemical breakers. The preferential channels also help reduce the influx of aqueous formation and/or injection fluids. This paper details the development of the RDF system and the engineering of it on two openhole gravel-pack completions in the East Wilmington Field off the coast of Long Beach, California. It discusses the development of the system and the field trials. A maintenance schedule used by the fluid engineers for anticipated potential problems is also discussed. The field performance is discussed and lessons learned are contrasted with conceptual design. Comparative data from earlier horizontal wells are included and contrasted with respect to the RDF system design, drilling parameters and well start-up. Finally, the initial well-test data are presented. Introduction In wells that are completed with open gravel packs, particular attention and study has been given to effects of the filter cake deposited on the sandstone reservoir. Depending on the chemical and physical nature of the filter cake, there can be detrimental impairment to both the producing reservoir and to the devised completion.[1–6] One of the primary functions of a Reservoir Drill-In Fluid (RDF) filter cake is to minimize both the invasion of the fluid's filtrate and drill solids into the intended producing zone. The deposition of an impermeable filter cake is critical in various reservoirs that have openhole completions where damage to the formation cannot be by-passed by perforating. The reservoir drilling fluid filter cake should be strong enough to prevent losses and premature screen out during the gravel pack process. After the gravel packing of the well is completed, the removal of the filter cake is desired to prevent plugging of the gravel pack and the completion screen. In low pressure reservoirs, filtercake removal could be especially necessary to prevent completion blockage. The preferred method employed to clean up the drilling fluid filter cake has been the use of chemical breakers such as oxidizers, acid, enzymes, a chelating agent solution or a combination of the latter two. Placement techniques for chemical breakers have included both post-gravel-pack and during the gravel pack. When post-gravel-pack placement occurs, sometimes there may be difficulty in treating the entire filter cake causing only localize treatment. If the chemical breaker is added during the gravel-pack operation, there may be a risk of premature filtercake breakthrough which could prevent the well from being completely packed with sand. External filtercake stimulation may not effectively contact all of the filter cake resulting in patchy filtercake dissolution. Breakthrough of aggressive chemical treatments may cause the migration of fines and chemicals into the formation under high differential pressure conditions. It is against this background that a new type of Reservoir Drill-In Fluid was designed utilizing the concept of an active filter cake whereby cleanup is initiated by the oil produced out of the reservoir instead of an external means. This Active Filtercake System still deposits a protective barrier across the formation; but instead of using a conventional starch fluid-loss-control agent and conventional calcium carbonate bridging material, it uses hydrophobic components that produce an organophilic filter cake. This organophilic filter cake provides channels through which hydrocarbons are travel through the gravel and then through the completion hardware into the production tubulars. The overall objective of the Active Filtercake System is to be non-damaging to both the reservoir and the completion.

A Specially Designed Organophilic Chloride-Free Reservoir Drill-In Fluid Meets the Challenges of the First Horizontal Well in Mozambique

“…The need for any external filtercake breaker for the purpose of dispersing or destroying the filtercake is thus eliminated. Ravitz et al (2005) documented the first use of the active filtercake system in Long Beach's Wilmington field. This RDF system was used first to drill the reservoir section of a horizontal well, and then the reservoir section of an S-shaped well.…”

Successful Implementation of Horizontal Open-Hole Gravel Packing in the Stybarrow Field, Offshore Western Australia

“…These materials create organophilic channels through the filtercake providing increased transmissibility for hydrocarbons (Ravitz et al 2005). This eliminated the need for post gravel pack well stimulation to remove the filtercake.…”