Influence of Formation Heterogeneity on Foam Flooding Performance

Petroleum Science https://doi.org/10.1007/s12182-019-00408-x ORIGINAL PAPER Infuence of formation heterogeneity on foam fooding performance using 2D and 3D models: an experimental study Ling‑Zhi Hu1,3 · Lin Sun1 · Jin‑Zhou Zhao1 · Peng Wei2 · Wan‑Fen Pu1 Received: 26 April 2019 © The Author(s) 2019 Abstract The formation heterogeneity is considered as one of the major factors limiting the application of foam fooding. In this paper, infuences of formation properties, such as permeability, permeability distribution, interlayer, sedimentary rhythm and 3D heterogeneity, on the mobility control capability and oil displacement efciency of foam fooding, were systematically investigated using 2D homogeneous and 2D/3D heterogeneous models under 120 °C and salinity of 20 × 104 mg/L. The fow resistance of foam was promoted as the permeability increased, which thus resulted in a considerable oil recovery behavior. In the scenario of the vertical heterogeneous formations, it was observed that the permeability of the high-permeable layer was crucial to foam mobility control, and the positive rhythm appeared favorable to improve the foam fooding performance. The additional oil recovery increased to about 40%. The interlayer was favorable for the increases in mobility reduction factor and oil recovery of foam fooding when the low permeability ratio was involved. For the 3D heterogeneous formations, foam could efciently adjust the areal and vertical heterogeneity through mobility control and gravity segregation, and thus enhancing the oil recovery to 11%–14%. The results derived from this work may provide some insight for the feld test designs of foam fooding. Keywords Foam fooding · Permeability ratio · 2D/3D models · Heterogeneity · Enhanced oil recovery 1 Introduction fow resistance created by foam in high-permeability zones could promote fuid diversion to the previously unswept The technical feasibility of foam fooding for enhanced oil zones, and the gravity diference appeared in the presence recovery (EOR) has been approved previously (Wei et al. of foam could help to sweep the upper part of reservoirs 2018; Zhang et al. 2010). It was recognized that the high (Ma et al. 2013; Pang et al. 2018). Meanwhile, owing to the viscoelastic liquid flms, the superposed gas bubbles could squeeze and pull oil droplets out of the dead end pores Edited by Yan-Hua Sun (Arnold and Wit 1990; Ashoori et al. 2011). Furthermore, the foam agents, which are surfactant-based materials, help * Lin Sun in reducing the interfacial tension between oil and water and [email protected] altering rocky wettability (Kamal 2016; Kumar et al. 2008; * Jin-Zhou Zhao Pu et al. 2016). Therefore, a foam fooding process is not [email protected] only capable of improving the sweep efciency but also able * Peng Wei to improve the microscopic displacement efciency, which [email protected] therefore results in a signifcantly high oil recovery factor 1 State Key Laboratory of Oil and Gas Reservoir Geology (Farajzadeh et al. 2009a, 2012; Shokrollahi et al. 2014). and Exploitation, Southwest Petroleum University, It was well-documented that the sweep efciency of foam Chengdu 610500, Sichuan, China fooding could be noticeably improved through screening 2 MOE Key Laboratory of Oil and Gas Fine Chemicals, foam agents and optimizing injected parameters (Hou et al. School of Chemistry and Chemical Engineering, Xinjiang 2013; Li et al. 2011; Liu et al. 2014; Wang et al. 2015). In University, Urumchi 830046, Xinjiang, China addition to the aforementioned, the physical properties of the 3 Yumen Oilfeld of Chinese National Petroleum Corp, formation also play a crucial role in foam fooding behavior. Yumen 735211, Gansu, China Vol.:(0123456789)1 3 Petroleum Science As some researchers claimed, the mobility reduction fac- of 99.9% (Xinju Co., Ltd). The foaming agent HTS was tor (MRF) that represents the mobility control capacity of synthesized in our laboratory, which was a mixture of gly- foam in the porous media is signifcantly improved with the coside surfactant and zwitterionic surfactant. Based on the increases in core permeability and core length (Farajzadeh Waring blender method, the foam volume and the half-life et al. 2009b; Wang et al. 2012; Zhao et al. 2012). In terms time of a 0.2% HTS solution were 580 mL and 185 s at of heterogeneous formations, foam creates a high sweep 120 °C. The interfacial tension between the 0.2% HTS efciency by diverting fuids to relatively low-permeable solution and the crude oil was 1.5 mN/m. Quartz sand was zones (Liu et al. 2008), especially for the positive rhythm supplied by Pixian Co., Ltd (Chengdu, China). The cores cases (Liu et al. 2010; Ma et al. 2013). Siddiqui et al. (1997) used in this work were artifcial cores mainly composed stated that fuid diversion can be enhanced by increasing the of quartz sand, and supplied by the Northeast Petroleum permeability ratio within a specifc range. While placing an University (Daqing, China). impermeable layer in the multilayer core, the crossfow and fuid diversion are both hindered in foam fooding. Although pioneering works have made great eforts to address the fac- 2.2 Experimental apparatus and procedures tors that infuence the foam sweep efciency, there are very limited studies of the impact of formation heterogeneity, The sand pack and 2D model tests were conducted at which is believed to be extremely important for design of 20 MPa and 120 °C. The 3D model tests were carried out foam fooding pilot in oilfelds. at 5 MPa and 120 °C. In all experiments, foam fooding Given this issue, the primary objective of this work is was carried out by co-injecting the nitrogen and foam solu- to systematically investigate the EOR performance of foam tion (0.2% HTS, foam quality was 0.67). fooding in diferent types of formations, and fgure out the infuence of formation structure on the foam fooding efciency. To accomplish this research objective, long sand 2.2.1 Sand pack tests packs, which had diferent permeabilities, were initially set up to examine the fow behavior of foam including mobility Figure 1 shows a schematic diagram of the apparatus control and fow resistance in the subsequent waterfood- for sand pack tests. Four pressure monitoring ports were ing. Thereafter, 2D homogeneous/heterogeneous cores were evenly distributed along the sand pack, which was flled used to study the efects of permeability, permeability dis- with quartz sand (70–140 mesh). The length and diameter tribution, interlayer and sedimentary rhythm on the foam of the sand packs were 100 cm and 2.5 cm, respectively. mobility control and oil recovery. Eventually, foam fooding The physical parameters of the sand packs are listed in tests were carried out in the 3D heterogeneous models to Table 2. comprehensively investigate the displacement behavior in The formation water was frst injected at 1.0 mL/min complex heterogeneous conditions. followed by foam injection. At each stage, the diferential pressure ∆Pwi of water and ∆Pf of foam at each sec- tion were recorded (Fig. 2) when four pressures changed 2 Experimental slightly. Thereafter, the corresponding mobility reduction factor (MRF) was calculated from Eq. (1). Formation 2.1 Materials water injection was resumed at the same rate (1.0 mL/ min), and the dynamic diferential pressure ∆Pswi was Crude oil and formation water were kindly provided by measured in order to obtain the residual resistance factor an oilfeld located in western China. The viscosity of the (RRF) from Eq. (2). crude oil was about 8.5 mPa s at 120 °C. The composi- ΔP MRF = ﬁ tion of formation water is given in Table 1. N2 had purity ΔPwi (1) Table 1 Composition of formation water Total salinity, mg/L Cation concentration Ccation, mg/L Anion concentration Canion, mg/L + + 2+ 2+ − 2− − K +Na Ca Mg Cl SO4 HCO3 204,672 67,430.31 10,279.6 1200.74 125,501.51 150 88.17 1 3 Petroleum Science Pressure sensing system Oven P1 P2 P3 P4 Data acquisition Sand pack Back pressure regulator n Nitroge brine Foam solution Crude oil Overburden Formation pump Gas flow controller Graduated ISCO pump separator Fig. 1 Schematic diagram of the apparatus for sand pack tests Table 2 Physical parameters of the sand packs used (a) Sand pack No. Porosity, % Water permeability, mD (b) 1 27.3 291 Low permeability layer 2 28.5 753 3 30.6 1105 High permeability layer 4 31.8 1592 (c) Low permeability layer Interlayer High permeability layer ΔP1 ΔP2 ΔP3 P1 P2 P3 P4 Fig. 3 Images of diferent cuboid cores. a Homogeneous core. b Front Middle Tail Two-layered heterogeneous core. c Two-layered heterogeneous core with an interlayer involved Flow direction 2.2.2 2D model tests Fig. 2 Diagram of pressure monitoring for sand pack tests. The red arrow points to the fow direction The apparatus for 2D model tests is analogous to Fig. 1 with the exception of the porous media. To simulate dif- ΔP RRF = swi ferent permeability properties, three types of cuboid cores ΔPwi (2) were prepared as shown in Fig. 3. For the multilayer core, the high permeability layer was placed at the bottom of the core holder to simulate the positive rhythm if not specifed. 1 3 Petroleum Science Table 3 Physical parameters of the homogeneous cores for oil displacement experiments Core No. Length, cm Cross-sectional area, cm2 Porosity, % Average gas permeability Initial oil Kg, mD saturation, % 11 29.90 19.98 16.02 200 63.3 12 30.01 20.10 18.17 300 71.7 13 29.30 19.93 23.30 700 65.3 14 29.41 19.78 28.03 1700 67.6 15 29.72 20.03 28.76 2000 69.5 Table 4 Physical parameters of the heterogeneous cores Experiment Notes Core No.

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