Snorre In-depth Water Diversion Using Sodium Silicate - Large Scale Interwell Field Pilot

Abstract

Here we report on in-depth water diversion using sodium silicate to increase oil recovery at the Snorre field, offshore Norway. A comprehensive qualification program revealed that the onset of gelation can be controlled; this was demonstrated in realistic core flood experiments as well as in a single well injection pilot. This paper highlights key design, response measurement plan and operational experiences from a large scale interwell field pilot of sodium silicate injection in a reservoir segment at the Snorre field on the Norwegian Continental Shelf. The operation of injecting 113 000 m 3 preflush, 240 000 m 3 sodium silicate and 49 000 m 3 postflush was performed from June to October 2013. The goal is to create an in-depth restriction between a subsea water injection well and a platform oil producer with approximately 2 000 m well spacing, and thereby improve the reservoir sweep by water injection.To perform the field pilot a 35 000 ton shuttle tanker was converted to a well stimulation vessel with the necessary equipment to accommodate a higher number of people, a desalination plant, storage and mixing equipment and high pressure pumps. The vessel was connected directly to a subsea water injection well and injected during a period of 5 months. The chosen design was to (a) soften the formation water by a KCl preflush, (b) control the gelation kinetics using HCl acid as activator, mixed into the diluted silicate solution and (c) displace the silicate solution by a KCl postflush followed by seawater injection.The pilot injection operation is completed, and the displacement of the sodium silicate with following seawater injection to the planned position for in-depth plugging is still on-going. The operational success criteria of proving ability to perform large scale transport, mixing and injection of sodium silicate from a shuttle tanker directly into a subsea well with no near wellbore plugging is met. Future production response will reveal if the success criteria of in-depth plugging, improved reservoir sweep and decrease in water cut will be met.

Rheological evaluation of a sodium silicate gel system for water management in mature, naturally-fractured oilfields

“…An in-depth permeability restriction of approximately 40 m away from the wellbore and permeability reduction of more than 100 were achieved and confirmed by post-gelation fluid injectivity measurements and transient falloff tests (Skrettingland et al, 2012). An inter-well field pilot conducted in 2013 on the same field demonstrated operational success to perform large-scale sodium silicate gelant injection with no wellbore plugging, and confirmed the ability to control the gelation onset (Skrettingland et al, 2014).…”

Optimization Of In-Depth Water Diversion Using A Fully Implicit Thermal-Compositional Approach

“…A number of pilot studies in the North Sea have demonstrated in recent years that sodium silicate can be successfully employed to enhance recovery from producing fields (Skrettingland et al (2012(Skrettingland et al ( , 2014). Combined with these pilots, experimental laboratory work has given insight on activation conditions, core-scale behaviour, and chemistry of the poorly understood polymerization process (Icopini et al (2005); Stavland et al (2011)).…”

“…Combined with these pilots, experimental laboratory work has given insight on activation conditions, core-scale behaviour, and chemistry of the poorly understood polymerization process (Icopini et al (2005); Stavland et al (2011)). Several numerical simulation studies, based on a weak coupling of a reservoir flow modeling and a separate software module for chemical reactions, have been able to replicate the main characteristics of the observed behaviour (Hiorth et al (2016); Skrettingland et al (2014)). Since the development of silicate gels and the accompanying permeability reduction is essentially a coupled process, Trujillo et al (2018) recently proposed a fully implicit coupled chemical-compositionalflow implementation.…”

Laboratory Testing of Environmentally Friendly Chemicals for Water Management

“…The combined use of silicate/polymer systems has been reported by Lakatos et al, (1999) for near wellbore matrix treatment but not for controlling water production in naturally fractured reservoirs. Stavland et al, (2011) conducted a laboratory evaluation of a silicate system for deep reservoir placement (Skrettingland et al, 2014(Skrettingland et al, , 2012; the laboratory results were modeled using a commercial simulator (Hatzignatiou et al, 2014).…”

“…There are three field pilots on the NCS where sodium silicates have been used; one pilot on Gullfaks (Rolfsvåg et al, 1996), and two pilots on Snorre. The Snorre pilots include a one well (Skrettingland et al, 2012) and a two well pilots (Skrettingland et al, 2014). In these pilots, sodium silicate was placed in formation matrix, whereas our focus is on a high-conductivity fracture treatment (CNF reservoirs).…”