Plugging of Fractures in Chalk Reservoirs by Enzymatic Induced Calcium Carbonate Precipitation

Abstract

fax 01-972-952-9435. AbstractNatural or induced fractures in a chalk reservoir can significantly reduce the recovery from a field. Therefore, plugging of fractures with a wide range of materials has been investigated over the years. Calcium carbonate, being the main constituent of the reservoir itself, is an obvious candidate. In order to apply calcium carbonate as a plugging fluid, a mechanism for delaying the precipitation has previously been suggested in the literature. This mechanism involves enzymatically induced plugging based on the mechanism of the enzyme urease converting urea into ammonia and carbonate. When carbonate is formed, it will precipitate with calcium in solution forming calcium carbonate. However, the amount of produced calcium carbonate was relatively low and the costs of the used stabilizer and high purity enzyme source was prohibitively high for bulk use. Furthermore, the calcium carbonate was produced as a slurry of small particles, which is deemed less efficient for fracture plugging compared to larger crystals or aggregates.In this paper work on design of an improved plugging fluid based on enzymatic calcium carbonate precipitation and optimization towards a field applicable solution is presented. The relatively expensive stabilizer and enzyme source is replaced with a low cost ingredient, which also improves the rate of precipitation. By optimizing the concentrations of the reactants, we have improved the yield of calcium carbonate from the initial 20 g/L to more than 200 g/L. Furthermore, we have been able to control the crystallization and obtain much larger calcium carbonate crystals. Laboratory plugging experiments have shown that larger crystal sizes significantly improves the durability of the formed plugs.

Sand and silty-sand soil stabilization using bacterial enzyme–induced calcite precipitation (BEICP)

“… Further advancements with characterizing and optimizing the procurement, performance, D r a f t Nemati and Voordouw 2003;Nemati et al 2005Larsen et al 2008Bang et al 2009Yasuhara et al 2011Handley-Sidhu et al 2013Neupane et al 2013, 2015ab Hamdan et al 2013b Hamdan et al , 2016Kavazanjian and Hamdan 2015;Kavazanjian et al 2017Nam et al 2014Park et al 2014Putra et al 2016 Un-treated Note: a average; b standard deviation; c relative error necessary for log-based plots (Baird 1994); d not analyzed…”

The Development of Novel Down-Hole Intervention Tools, a Change in Well Technology

“…The same two component system could be used to close of the sliding side doors or even holes, created by erosion or corrosion, in tubing or liners. (Ref: figure 9, Larsen, 2008) The second breakthrough was initiated by an article (Ravilious, 2004), whereby the growth of carbonates, when exposed to acids, was explained and supported by real life examples and tests. This initiated the development of the method to 'grow' precipitates in a facture which will result in filling up the fracture and therewith close it off.…”

“…An alternative to this method is described in SPE 108589. (Larsen, 2008) The third breakthrough Ask your drilling manager to abandon a well and he will pull the tubing, pull or drill out the production packer. Set a packer on top of formation, followed by a series of cement plugs and packers.…”

Biocementation of Calcareous Beach Sand Using Enzymatic Calcium Carbonate Precipitation

“…Calcium carbonate (CaCO 3 ) can cement the soil particles by precipitating at the particle-to-particle contact points or increase the particle roughness by precipitating at the particle surface. EICP has been studied for different applications, such as strengthening granular soil [1][2][3][4][5][6][7], reducing the hydraulic conductivity of granular soil [8][9][10], fugitive dust mitigation [11][12][13], sealing cracks in concrete [14], and removal of heavy metal ions [15].…”