Sweep Improvement Options for Highly Heterogeneous Reservoirs with High Temperature and Ultra-High Salinity: A Case Study in Tarim Basin, China

2021 ◽  
Author(s):  
Chengdong Yuan ◽  
Wanfen Pu ◽  
Mikhail Alekseevich Varfolomeev ◽  
Aidar Zamilevich Mustafin ◽  
Tao Tan ◽  
...  
Keyword(s):  
High Temperature ◽  
Oil Recovery ◽  
Tarim Basin ◽  
High Salinity ◽  
Mobility Control ◽  
Surfactant Flooding ◽  
High Permeability ◽  
Permeability Heterogeneity ◽  
Foam Flooding

Abstract How to control excessive water production in high-temperature and high-salinity reservoirs has always been a challenge, which has been facing many oil reservoirs in Tarim Basin (China), such as Y2 reservoir with an average temperature of 107 ℃, salinity of 213900 mg/L (Ca2++Mg2+>11300mg/L), and permeability from 2 to 2048 mD. In this work, we present experimental studies to determine the potential EOR process for Y2 reservoir from foam flooding, polymer gel/foam flooding, and microgel/surfactant flooding. To simulate the permeability heterogeneity of Y2 reservoir, a 2-D sand-pack model was used for flooding experiments. Vertically, three layers (first 0.6cm, second 0.8cm and third 1.6cm from top to bottom, respectively) were packed with different size sand to simulate permeability heterogeneity (permeability increases from first to third layer). A 0.3 cm higher permeability zone was also filled inside third layer. Horizontally, permeability gradually decreases from middle to two sides. In this model, injection well was vertical, and production well was horizontal. The effect of impermeable interlayer was also studied by isolating the second and third layer. The results show that conformance treatments using in-situ crosslinked gel or micro-gel are necessary before foam or surfactant injection under a high permeability heterogeneity. When an impermeable interlayer existed between the second and third layer, the additional oil recovery of N2 foam flooding, in-situ crosslinked gel/N2 foam flooding, and microgel/surfactant flooding was 16.34%, 20.37%, 17.50%, respectively, which was much higher than that without impermeable interlayer (9.84%, 13.62%, 12.07%). This implies that when multiple layers exist, crossflow between layers is unfavorable for improving oil recovery, which should be paid extra attention in EOR process. Foam flooding has not only a good mobility control capacity but also a good oil displacement ability (verified by visual observations of washed sand after experiments), which, together with the strong conformance control ability of crosslinked gel, makes in-situ crosslinked gel/N2 foam flooding yield the highest displacement efficiency. Generally, for high-temperature and ultra-high-salinity reservoirs with strong heterogeneity like Y2 reservoir, in-situ crosslinked gel/foam flooding can be a good candidate for EOR. This work provides a potential EOR method with high efficiency, i.e. in-situ crosslinked gel assisted N2 foam flooding, for the development of similar reservoirs like Y2 with high temperature, ultra-high salinity, high heterogeneity and multiple layers. Moreover, this work also highlights that, despite that foam has the ability of mobility and profile control, a conformance treatment is necessary to block high permeability zone before foam injection when the reservoirs has a strong heterogeneity.

Low-IFT Foaming System for Enhanced Oil Recovery in Highly Heterogeneous/Fractured Oil-Wet Carbonate Reservoirs

SPE Journal ◽  
2018 ◽  
Vol 23 (06) ◽  
pp. 2243-2259 ◽  
Author(s):  
Pengfei Dong ◽  
Maura Puerto ◽  
Guoqing Jian ◽  
Kun Ma ◽  
Khalid Mateen ◽  
...  
Keyword(s):  
Oil Recovery ◽  
Fractured Reservoirs ◽  
Surfactant Solution ◽  
Capillary Forces ◽  
Mobility Control ◽  
Carbonate Reservoirs ◽  
Residual Oil ◽  
High Permeability ◽  
The Matrix ◽  
Foam Flooding

Summary Oil recovery in heterogeneous carbonate reservoirs is typically inefficient because of the presence of high-permeability fracture networks and unfavorable capillary forces within the oil-wet matrix. Foam, as a mobility-control agent, has been proposed to mitigate the effect of reservoir heterogeneity by diverting injected fluids from the high-permeability fractured zones into the low-permeability unswept rock matrix, hence improving the sweep efficiency. This paper describes the use of a low-interfacial-tension (low-IFT) foaming formulation to improve oil recovery in highly heterogeneous/fractured oil-wet carbonate reservoirs. This formulation provides both mobility control and oil/water IFT reduction to overcome the unfavorable capillary forces preventing invading fluids from entering an oil-filled matrix. Thus, as expected, the combination of mobility control and low-IFT significantly improves oil recovery compared with either foam or surfactant flooding. A three-component surfactant formulation was tailored using phase-behavior tests with seawater and crude oil from a targeted reservoir. The optimized formulation simultaneously can generate IFT of 10−2 mN/m and strong foam in porous media when oil is present. Foam flooding was investigated in a representative fractured core system, in which a well-defined fracture was created by splitting the core lengthwise and precisely controlling the fracture aperture by applying a specific confining pressure. The foam-flooding experiments reveal that, in an oil-wet fractured Edward Brown dolomite, our low-IFT foaming formulation recovers approximately 72% original oil in place (OOIP), whereas waterflooding recovers only less than 2% OOIP; moreover, the residual oil saturation in the matrix was lowered by more than 20% compared with a foaming formulation lacking a low-IFT property. Coreflood results also indicate that the low-IFT foam diverts primarily the aqueous surfactant solution into the matrix because of (1) mobility reduction caused by foam in the fracture, (2) significantly lower capillary entry pressure for surfactant solution compared with gas, and (3) increasing the water relative permeability in the matrix by decreasing the residual oil. The selective diversion effect of this low-IFT foaming system effectively recovers the trapped oil, which cannot be recovered with single surfactant or high-IFT foaming formulations applied to highly heterogeneous or fractured reservoirs.

Carbon Dots Stabilized Foam for Enhanced Oil Recovery

2021 ◽  
Author(s):  
Sivabalan Sakthivel ◽  
Mazen Kanj
Keyword(s):  
Oil Recovery ◽  
Oil And Gas ◽  
High Salinity ◽  
Foam Stability ◽  
Surfactant Solution ◽  
Oil And Gas Industry ◽  
Mobility Control ◽  
Carbon Nanodots ◽  
High Permeability ◽  
Drainage Rate

Abstract Foams are the divergent fluids that are employed in the upstream oil and gas industry to reduce fluid channeling and fingering in the high permeability region. Foams are usually generated in the high permeability reservoirs (e.g. glass beads) by the alternative injection of surfactant and gas. Conventional foaming systems exhibit stability issues at the high temperature and high salinity reservoir conditions. In this investigation, we study the stability and efficiency (in terms of both enhanced inflow performance and added oil recovery) of foams formed using surfactant solution with and without carbon Nanodots (CND). The study involved using different brine salinities, CND concentrations, temperature and pressure conditions, and types of surfactants. A multifaceted interrelationship of the various influencing mechanisms is demonstrated. Foams are examined using foam analyzer, HP/HT coreflood and microfluidic setup. In trace amounts (5-10 ppm), CND contributed to 60-70% improvement in foam stability in high salinity brine. The improvement is attributed by the reduction of the drainage rate of the lamellae and a delay of the bubble rupturing point. Both microfluidic and core-flood experiments showed noticeable improvement in mobility control with the addition of the CND. This is contributed to an improved foamability, morphology, strength, and stability of the foam.

An Experimental Investigation of In Situ Combustion in High Permeability Contrast Systems

2021 ◽  
pp. 1-13
Author(s):  
Melek Deniz Paker ◽  
Murat Cinar
Keyword(s):  
Oil Recovery ◽  
Heavy Oil ◽  
Combustion Front ◽  
Fractured Reservoirs ◽  
Front Propagation ◽  
High Permeability ◽  
Vertical Orientation ◽  
In Situ Combustion ◽  
Horizontal Orientation

Abstract A significant portion of world oil reserves reside in naturally fractured reservoirs and a considerable amount of these resources includes heavy oil and bitumen. Thermal enhanced oil recovery methods (EOR) are mostly applied in heavy oil reservoirs to improve oil recovery. In situ combustion (/SC) is one of the thermal EOR methods that could be applicable in a variety of reservoirs. Unlike steam, heat is generated in situ due to the injection of air or oxygen enriched air into a reservoir. Energy is provided by multi-step reactions between oxygen and the fuel at particular temperatures underground. This method upgrades the oil in situ while the heaviest fraction of the oil is burned during the process. The application of /SC in fractured reservoirs is challenging since the injected air would flow through the fracture and a small portion of oil in the/near fracture would react with the injected air. Only a few researchers have studied /SC in fractured or high permeability contrast systems experimentally. For in situ combustion to be applied in fractured systems in an efficient way, the underlying mechanism needs to be understood. In this study, the major focus is permeability variation that is the most prominent feature of fractured systems. The effect of orientation and width of the region with higher permeability on the sustainability of front propagation are studied. The contrast in permeability was experimentally simulated with sand of different particle size. These higher permeability regions are analogous to fractures within a naturally fractured rock. Several /SC tests with sand-pack were carried out to obtain a better understanding of the effect of horizontal vertical, and combined (both vertical and horizontal) orientation of the high permeability region with respect to airflow to investigate the conditions that are required for a self-sustained front propagation and to understand the fundamental behavior. Within the experimental conditions of the study, the test results showed that combustion front propagated faster in the higher permeability region. In addition, horizontal orientation almost had no effect on the sustainability of the front; however, it affected oxygen consumption, temperature, and velocity of the front. On the contrary, the vertical orientation of the higher permeability region had a profound effect on the sustainability of the combustion front. The combustion behavior was poorer for the tests with vertical orientation, yet the produced oil AP/ gravity was higher. Based on the experimental results a mechanism has been proposed to explain the behavior of combustion front in systems with high permeability contrast.

scholarly journals Modification of Xanthan Gum for a High-Temperature and High-Salinity Reservoir

Polymers ◽  
2021 ◽  
Vol 13 (23) ◽  
pp. 4212
Author(s):  
Mohamed Said ◽  
Bashirul Haq ◽  
Dhafer Al Shehri ◽  
Mohammad Mizanur Rahman ◽  
Nasiru Salahu Muhammed ◽  
...  
Keyword(s):  
High Temperature ◽  
Oil Recovery ◽  
Xanthan Gum ◽  
Elevated Temperatures ◽  
High Salinity ◽  
Residual Oil ◽  
Core Flooding ◽  
Nacl Solution ◽  
The Core ◽  
Tertiary Oil Recovery

Tertiary oil recovery, commonly known as enhanced oil recovery (EOR), is performed when secondary recovery is no longer economically viable. Polymer flooding is one of the EOR methods that improves the viscosity of injected water and boosts oil recovery. Xanthan gum is a relatively cheap biopolymer and is suitable for oil recovery at limited temperatures and salinities. This work aims to modify xanthan gum to improve its viscosity for high-temperature and high-salinity reservoirs. The xanthan gum was reacted with acrylic acid in the presence of a catalyst in order to form xanthan acrylate. The chemical structure of the xanthan acrylate was verified by FT-IR and NMR analysis. The discovery hybrid rheometer (DHR) confirmed that the viscosity of the modified xanthan gum was improved at elevated temperatures, which was reflected in the core flood experiment. Two core flooding experiments were conducted using six-inch sandstone core plugs and Arabian light crude oil. The first formulation—the xanthan gum with 3% NaCl solution—recovered 14% of the residual oil from the core. In contrast, the modified xanthan gum with 3% NaCl solution recovered about 19% of the residual oil, which was 5% higher than the original xanthan gum. The xanthan gum acrylate is therefore more effective at boosting tertiary oil recovery in the sandstone core.

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