Controls losses in Depleted Reservoirs and high-permeability formations using Nanomaterial as a new mud product

Author's Department

Petroleum & Energy Engineering Department

Document Type

Research Article

Publication Title

Life Science Journal

Publication Date

12-28-2012

Abstract

Losses of whole mud to subsurface formations is called lost circulation or lost returns. Lost circulation has historically been one of the primary contributors to high mud costs. Other hole problems such as wellbore instability, stuck pipe and even blowouts have been the result of lost circulation. Besides the obvious benefits of maintaining circulation, preventing or curing mud losses is important to other drilling objectives such as obtaining good quality formation evaluation and achieving an effective primary cement bond on casing. The severity of losses ranges from minor seepage to complete losses with no returns regardless of the technique utilized to cure the problem. Under-balanced drilling1 with aerated fluids, foams or density-reducing beads has been successful in many areas. Injection of compressed air or nitrogen is usually necessary to accomplish the density reduction needed to achieve under-balanced conditions. Besides minimizing or preventing lost circulation, these techniques are also used to provide enhanced penetration rates and reduce formation damage due to invasion of drilling fluids or filtrate. In this study, novel fluids as Aphron drilling Nano-fluid have three chief attributes that serve to minimize fluid invasion and damage of producing formations. First, the base fluid is very shear thinning and not very thixotropic, exhibiting an extraordinarily high low-shear-rate viscosity (LSRV) and flat gels; the unique viscosity profile is thought to reduce the flow rate of the fluid dramatically upon entering a loss zone. Second, various components in the mud interact to produce micro-gels that help to reduce spurt loss. Finally, very tough and flexible micro-bubbles, called "Aphrons," create a soft seal within the permeable or fractured formation to reduce losses further. Aphron drilling fluids, which are highly shearthinning water-based fluids containing stabilized air-filled bubbles (Aphrons), have been applied successfully worldwide to drill depleted reservoirs and other high-permeability formations as well as fracture Granite formations. Based on laboratory determinations, the smallest size for a gas-core Aphron is 25 μm. The bubbles smaller than this size are not able to maintain the surfactant-based boundary separating them from the bulk water and thus get dispersed in the continuous water phase. From field study, Aphron ICS mud was used to drill KHA 403 and 404 wells (Yamen) compared to previous wells drilled with a polymer mud. The total volume of Aphron drilling fluid built to drill the reservoir interval was 696m3, and losses incurred totaled 265 m3 into formation fractures. A subsequent well, KHA 404, was drilled in the same area with the APHRON ICS mud, and it experienced no losses of the APHRON ICS mud and even greater production. Hydraulics relative to offset wells drilled with simple water-based polymer muds, it is reported that hole cleaning was substantially improved, even during periods when pump rate had to be reduced in an effort to mitigate downhole losses, indicating minimal invasion of drilled solids into the fractures drilled.

First Page

161

Last Page

170

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