Taking advantage of injectivity decline for improved recovery during waterflood with horizontal wells Pavel G. Bedrikovetsky a, ⁎, Thi K.P. Nguyen a , Andrew Hage a , John R. Ciccarelli a , Mohammad ab Wahab a , Gladys Chang b , Antonio Luiz S. de Souza c , Claudio A. Furtado c a University of Adelaide, Australian School of Petroleum, North Terrace, Santos Petroleum Engineering Blg, Adelaide, SA 5005, Australia b Schlumberger, Australia c Petrobras, Brazil abstract article info Article history: Received 3 November 2009 Accepted 23 May 2011 Available online xxxx Keywords: Injectivity Raw water PWRI Waterflooding Sweep efficiency Waterflood simulation Injectivity formation damage with waterflooding using sea/produced water has been widely reported in the North Sea, the Gulf of Mexico and the Campos Basin in Brazil. The damage is due to the capture of solid and/or liquid particles by reservoir rock that consequently leads to the permeability decline. Another reason for the permeability decline is the formation of a low permeable external filter cake. However, moderate injectivity decline is not too damaging for a waterflood project with long horizontal injectors, where the initial injectivity index is high. In this case, the injection of raw or poorly treated water may significantly reduce the cost of water treatment, which is a cumbersome and expensive procedure in offshore projects. In this paper we investigate the effects of injected water quality on waterflooding using horizontal wells. An analytical model for injectivity decline, which accounts for particle capture and a low permeable external filter cake formation, has been implemented into black oil reservoir simulator. It was found that induced injectivity damage results in a noticeable reduction of water cut and in increased (although delayed) sweep efficiency. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Injectivity decline is a widely spread phenomenon in waterflood projects. Usually it occurs due to the injected water containing solid and liquid particles. Particle capture by the rock decreases the permeability and the formation of an external filter cake on the well surface increases the hydraulic resistivity of the system (Pang and Sharma, 1997; Ochi et al., 1999; Al-Abduwani et al., 2005a). Both phenomena result in the decline of well index. The injectivity decline occurs during seawater injection, re-injection of produced water (PWRI) and injection of any poor quality water (Nabzar et al., 1996, 1997; Chauveteau et al., 1998; Rousseau et al., 2007). The injectivity damage can be prevented or mitigated by injected water treatment, which is an extremely expensive operation under offshore conditions. Water treatment costs remain high even with the relocation of treatment facilities onto the sea floor. The subject of cost reduction for injected water treatment is becoming of extreme importance worldwide due to increasing oil production by water- flooding, especially from offshore deep-water oil fields. The formation damage, induced by the captured particles and filter cake, leads to the homogenisation of the injectivity profile (Khambharatana et al., 1997, 1998) and decreases residual oil saturation (Soo and Radke, 1986a,b). Yet, it was found that the particle retention phenomena take place within a close vicinity of injection wells. In the case of vertical injectors used in thin layer-cake reservoir, the injected water bypasses the damaged zone near to the vertical injector by moving vertically along a short distance from low permeability to high permeability layer. The perturbation of the stream line system due to the induced formation damage is minimal. So, the un- uniformly distributed skin, induced along the vertical well, almost do not affect the oil-water flow away from the injector. Therefore, the injectivity profile homogenization has a little effect on sweep efficiency for the case of vertical wells in layer-cake reservoirs. For long horizontal wells, where the well length have the same order of magnitude as the inter-well distance, it would take much longer for water to bypass the damaged zone by moving “parallel” to the injector in order to enter the faster flow path. So, it is expected that the injectivity profile homogenization may result in more significant sweep increase in a Journal of Petroleum Science and Engineering 78 (2011) 288–303 ⁎ Corresponding author. Tel.: + 61 883033082. E-mail address: pavel.russia@gmail.com (P.G. Bedrikovetsky). 0920-4105/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.petrol.2011.05.020 Contents lists available at ScienceDirect Journal of Petroleum Science and Engineering journal homepage: www.elsevier.com/locate/petrol