Low Salinity Water Flooding: Proof Of Wettability Alteration On A Field Wide Scale

Abstract

Summary Low salinity water injection is an emerging EOR technology, applicable to mixed-to-oil-wet sandstone reservoirs. Flooding with low salinity water causes desorption of petroleum heavy ends from the clays present on the pore wall, resulting in a more waterwet rock surface, a lower remaining oil saturation and higher oil recovery. A secondary flood application is discussed in the Omar field in Syria showing a change of wettability from oil wet to a water-wet system. This change in wettability is supported by the observation of dual steps in watercut development. In between the two steps the watercut was constant. This behaviour is a known indicator of changing wettability. Moreover, direct connate water banking measurements confirm the change. The field observations are supported by spontaneous imbibition experiments in core material and a single well Log-Inject-Log test in an analogue field. From the field observations, the change in wettability is estimated to be nearly complete, leading to an associated incremental recovery of 10–15% of the Stock Tank Oil Initialy In Place (STOIIP). The significance of this work is that this is one of the very few documented proofs of concept on a reservoir scale. Work is ongoing to prove this concept in a tertiary flood as well.

Effect of injection brine composition on wettability and oil recovery in sandstone reservoirs

“…In the recent years, extensive laboratory and field tests have showed that LSF can act as an attractive enhanced oil recovery technology [1][2][3][4][5][6]. The popularity of this technology is mainly because of its efficiency in displacing crude oil, low investment, easy operation, ease of injection, and environmental protection, all of which bring economic benefits compared to other chemical EOR methods [7].…”

“…Over the last decades, the wettability alteration has been widely believed to be an important contributor to LSF [1,5,7,10]. Wettability alteration of sandstone rocks by LSF is related to the minerals on sandstone surface, the polar components in crude oil and the ion composition of injected water [8,11,12].…”

“…Ca 2+ ) in the aqueous solutions act like a bridge between the negatively charged sites on substrate surface and negatively charged polar groups in crude oil, opposing desorption. From the field observation, LSF in the Omar field in Syria results in a more water-wet rock surface, which leads to an incremental recovery of 10-15% of the Stock Tank Oil Initially In Place (STOIIP) [1].…”

An Efficient Approach for the Determination of Oil Production Rate During the Water-flooding Recovery Method

“…Advanced enhanced oil recovery (EOR) techniques are more costly and complex in comparison with water-flooding method. Moreover, low salinity water flooding is emerging as one of the promising recovery methods (Vledder et al, 2010). Advances in technology will enable the maximization of water injection before developing advanced EOR methods (Al-Mutairi and Kokal, 2011).…”

A study of water chemistry extends the benefits of using silica-based nanoparticles on enhanced oil recovery

“…Skauge (2013) identified critical parameters to describe low salinity mechanisms in sandstone such as multi-component ionic exchange, fines migration, wettability alteration, electrical double layer effects, microscopically diverted flow and pH-driven wettability alteration. Dang et al (2013) considered that the most reliable mechanism among these proposed mechanisms is the wettability modification toward a more waterwetting state, as observed by Jadhunandan and Morrow (1995); Tang and Morrow 1999a;Israelachvili (2002, 2004);Vledder et al (2010);and Zekri et al (2011). In addition, ionic exchange among the injected water, the formation water and mineral dissolution/precipitation products in low salinity water can lead to the adsorption of divalent ions and promote mineral dissolution, thereby altering the wettability.…”