Abdulmohsin Imqam

Preformed-Particle-Gel Extrusion Through Open Conduits During Conformance-Control Treatments

Millimeter-sized (10 um~mm) preformed particle gels (PPGs) have been used successfully as conformance control agents in more than 5,000 wells. They help to control both water and CO2 production through high-permeability streaks or conduits (large pore openings), which naturally exist or are aggravated either by mineral solutions or by a high injection pressure during the flooding process. This paper explores several factors that can have an important impact on the injectivity and plugging efficiency of PPGs in these conduits. Extensive experiments were conducted to examine the effect of the conduit’s opening size and the PPG strength on the ratio of the particle size to the opening diameter, injectivity index, resistance factor, and plugging efficiency. Five-foot tubes with four internal diameters were designed to emulate the opening conduits. Three pressure taps were mounted along the tubes to monitor PPG transport and plugging performance. The results show that weak gel has less injection pressure at a large particle opening ratio compared to strong gel. PPG strength impacted injectivity more significantly than did particle opening ratio. Resistance factor increased as the brine concentration and conduit opening size increased. PPGs can significantly reduce the permeability of an open conduit and their plugging efficiency depends highly on the particle strength and the conduit’s opening size. The particle size of PPG was reduced during their transport through conduits. Experimental results confirm that the size reduction was caused by both dehydration and breakdown. Based on the lab data, two mathematical models were developed to quantitatively calculate the resistance factor and the stable injection pressure as a function of the particle strength, particle opening ratio, and shear rate. This research provides significant insight into designing better millimeter-sized particle gel treatments intended for use in large openings, including open fractures, caves, worm holes, and conduits. Introduction Excess water production in oil fields is becoming a challenging economical and environmental problem as more reservoirs are maturing. An estimated average of three barrels of water are produced for each barrel of oil produced worldwide (Bailey et al., 2000). It is estimated that the total cost to separate, treat, and dispose of this water is approximately

Transport of Nanogel through Porous Media and Its Resistance to Water Flow

50 billion per year (Hill et al., 2012). Water can flow into the wellbore as a result of either near-wellbore problems or reservoirrelated problems (Seright et al., 2001). The mechanisms that contribute to this undesired water production must be fully understood before the appropriate treatment can be chosen. Water channeling, one of the primary reservoir conformance problems, is caused by reservoir heterogeneities that lead to the development of high-permeability streaks. These streaks include open fractures and fracture like features, such as caves, worm holes, and conduits (Smith et al, 2006). These highconductivity areas inside the reservoir only occupy a small fraction of the reservoir but will capture a significant portion of injected water. As a result, large amounts of oil remain unswept as a large water flood will bypass oil-rich unswept zones/areas. Gel treatments have been proven to be a cost-effective chemical conformance control technology to reduce the fluid flow in these large opening features. The application of these technologies can not only control water production but also significantly increase the oil production and extend the economic life of a reservoir. Traditionally, in-situ bulk gels have been used for this purpose. However, preformed particle gels recently have attracted much attention because they can solve some of the problems associated with in-situ gel systems, such as the dilution and dispersion of the gelant, chromatographic separation of the gelant solution, and so on. (Chauveteau et al., 2001, 2003; Coste et al., 2000; Bai et al., 2007a, 2007b).

Optimizing the strength and size of preformed particle gels for better conformance control treatment

The application of nanoparticles in enhanced oil recovery (EOR) continues to gain attention in the oil industry due to its apparent potential. However, previous studies have focused on the evaluation of stiff particles, such as silica and aluminum oxide. In this paper, we present our experimental results of deformable nanoparticle transport behavior through porous media. Nanogel particles with sizes ranging from 100-285 nm were used to represent deformable nanoparticles. Core flooding tests were run using sandstone cores with water permeabilities ranging from 42 to 1,038 mD. We investigated the effects of the permeability, particle concentration, particle deformability, and flow rate on the particle propagation, resistance factor, and residual resistance factor (permeability reduction factor). The results show that the resistance factor ranged from 5 to 14 for rocks with permeabilities higher than 311 mD, indicating that the nanoparticles were able to transport easily through these rocks. However, the resistance increased to 383 when the permeability was as low as 41.2 mD, indicating that the nanogel could not penetrate the rock easily. After placing the particles, brine was injected at different flow rates. The results indicate that the nanoparticles effectively reduced the permeability of the rocks with the original permeabilities of 143 to 555.4 mD, but the residual resistance factor of the high-permeability rock (1,038 mD) was relatively small, ranging from 2.67 to 4.39. The resistance factor and residual resistance factor increased with the particle concentration and decreased with the flow rate, and both factors can be well fitted using power law equations as a function of velocity. The nanogel adsorption layer thickness decreased with the shear rate. Introduction Water usually is injected into reservoirs as a secondary recovery method to maintain the reservoir pressure and displace oil. In wells nearing the end of their productive lives, about 2/3 of the oil remains underground, but water can constitute as much as 98% of the liquid brought to the surface. Enhanced oil recovery (EOR) methods often are implemented to increase oil recovery and reduce water production [Fletcher et al., 2010]. EOR methods improve oil recovery commonly through the following three primary mechanisms: (1) they mobilize residual oil by increasing the capillary number through interfacial tension (IFT) reduction and/or wettability modification methods, (2) they decrease the mobility ratio by adding polymer into the water to increase its viscosity, and (3) they improve conformance in heterogeneous reservoirs for better sweep efficiency by reducing the permeability of high-permeability zones or streaks [Hite et al., 2005; Lake et al., 1992; Thomas, 2005; Fletcher et al., 2010]. Many different chemical EOR materials exist that can be used to reduce permeability and improve conformance in reservoirs with high-permeability streaks and fractures, thus reducing water production. Gel treatment has been proven to be a cost-effective method for conformance control [Bai et al., 2013]. Several researchers have proposed methods that employ particle gels to homogenize reservoirs and control undesired water production (known as water shutoff). The particle gels include preformed particle gels (PPGs) [Bai et al., 2004], microgels [Chauveteau et al., 2000; Rousseau et al., 2005; Zaitoun et al., 2007], pH-sensitive gels [Al-anazi et al., 2002; Huh et al., 2005], and temperature-sensitive submicron-sized polymer (bright water) [Pritchett et al., 2003; Frampton et al., 2004]. These particles differ primarily in their size [Bai et al., 2013]. Several publications have noted that PPG, microgels, and submicron-sized particles have been implemented economically to decrease water production from mature oil fields. For example, PPGs have been applied successfully in more than 5,000 wells [Bai et al, 2013]. Microgels have been applied in 10 gas storage wells to decrease water production [Zaitoun, 2007]. Submicrogels (namely, bright water) have been used in more than 60 wells to divert in-depth fluid flow [Cheung, 2007, Mustoni 2010].