"Micro-Bubbles": New Aphron Drill-In Fluid Technique Reduces Formation Damage in Horizontal Wells

Abstract

Tom Brookey, SPE, Acti Systems, Inc. Abstract Horizontal drilling technology has enhanced production through increased ability to expose formation openings. In most cases, these openings are fractured, vugular, or otherwise highly permeable. Many are drilled through low-pressure reservoirs where drilling fluid losses occur and often cause severe formation damage. The use of conventional lost circulation control materials are restricted due to the downhole tools required, and borehole sealing techniques are mostly ineffective in this type of application. A novel new drill-in fluid is being used to drill horizontal and high angle wells through these damage-prone reservoirs. This fluid combines certain surfactants and polymers to create a system of "micro-bubbles" known as aphrons encapsulated in a uniquely viscosified system. These aphrons are non- coalescing and recirculatable so that density reduction is accomplished without expensive air or gas injection. A unique feature of the micro-bubble network, stopping or slowing the entry of fluids into the formation, creates downhole bridging. The unique viscosity builds to create a resistance to movement into and through the zone so that a true noninvasive, at-balance fluid is achieved. Test data shows the enhanced hole cleaning and suspension properties. Case histories show that drilling problems are reduced, mud losses are prevented, and completions are simplified. Natural production was achieved in many cases. No problems with formation damage or inhibited production were seen. P. 645

Herschel–Bulkley rheological parameters of lightweight colloidal gas aphron (CGA) based fluids

“…In response to environmental concerns, XG presents good properties for drilling muds application (Arabloo et al, 2012b). Brookey (1998) found XG biopolymer is the most effective viscosifier in stabilizing the aphrons in CGA based drilling fluids. Concentrations of 0.286-0.571% (w/v) XG were used in this study.…”

“…Finally, aphrons with cores formed of a waterin-oil emulsion are called colloidal emulsion aphrons (Deng et al, 2005). Currently, the use of CGA based fluids is increasing rapidly in the petroleum industry because these fluids exhibit properties that are desirable in many field operations (Brookey, 1998;Gregoire et al, 2005;Ivan et al, 2001;Ramirez et al, 2002;Rea et al, 2003;White et al, 2003). The potential of aphrons as components of drilling fluids rests in their ability to form a solid free, tough, and elastic internal bridge in pore networks or fractures to minimize deep invasion by means of air microbubbles (Belkin et al, 2005;Growcock et al, 2003).…”

“…The use of CGAs as a drilling/completion fluid also presents several advantages. The high carrying capacity, the minimum amount of fluid placed in the formation, and the excellent fluid recovery after treatment are some of the advantages that CGA based fluids present when used during operations (Brookey, 1998;Growcock et al, 2006). The major implementation of rheological parameters for evaluating drilling fluid behavior are in solving problems of hydraulic calculations, suspension of cuttings and hole cleaning (Arabloo et al, 2012b).…”

Mathematical modeling of the Colloidal Gas Aphron transport through porous medium using the filtration theory

“…Recently, Aphron fluids have been successfully employed in drilling depleted reservoirs or formations which had previously experienced huge fluid losses (Brookey, 1998) (Ivan et al, 2001) (Ramirez et al, 2002) (Bjorndalen and Kuru, 2008). Brookey was the first one who introduced Aphrons for horizontal well drilling.…”

“…In this type of drilling operation, fluid pressure must be maintained at a higher level than the formation pressure, but the pressure difference must not be so high to avoid fluid invasion into the formation rock (Belkin et al, 2005). Although more experimental investigation is carried out on Aphron fluid filtration and its related parameters (Sebba, 1987) (Brookey, 1998) (Ivan et al, 2001) (Ramirez et al, 2002) (Bjorndalen and Kuru, 2008), a few modeling works were carried out in the literature (Belkin et al, 2005), recently Alizadeh and Khamehch have published some works on the Aphron modeling and flow through porous medium (Alizadeh and Khamehchi, 2015a) (Alizadeh and Khamehchi, 2015b) (Alizadeh and Khamehchi, 2016a) (Alizadeh and Khamehchi, 2016b) (Alizadeh and Khamehchi, 2016c) When a solid free fluid is created due to environmental issues, the use of Aphron drilling fluids is considered. Bridging in the front of the porous media in near wellbore zone, in fractured or depleted reservoirs, reduces the formation damage and fluid depth of invasion into the formation.…”