Tian, Ye (Colorado School of Mines) | Xiong, Yi (Colorado School of Mines) | Wang, Lei (Colorado School of Mines) | Lei, Zhengdong (Research Institute of Petroleum Exploration and Development, PetroChina) | Zhang, Yuan (Research Institute of Petroleum Exploration and Development, PetroChina) | Yin, Xiaolong (Colorado School of Mines) | Wu, Yu-Shu (Colorado School of Mines)
Gas injection has become the top choice for IOR/EOR pilots in tight oil reservoirs because of its high injectivity. The effects of nanoconfinement and geomechanics are generally considered as non-negligible, but its coupled effects and resulting flow and displacement are still not well understood for gas injection. We hence present a general compositional model and simulator to investigate the complicated multiphase and multicomponent behaviors during gas injection in tight oil reservoirs.
This compositional model is able to account for vital physics in unconventional reservoirs, including nanopore confinement, molecular diffusion, rock-compaction, and non-Darcy flow. The MINC method is implemented to handle fractured media. The nanopore confinement effect is modeled by including capillarity in VLE calculations. The rock compaction effect is represented by solving the mean stress from a governing geomechanical equation which is fully coupled with the mass balance equations to ensure the numerical stability as well as a physically correct solution. The equations are discretized with integral finite difference method and then solved numerically by Newton's method.
The simulator is validated against a commercial compositional software (CMG-GEM) before it is applied to simulate gas injection. Huff-n-puff with dry gas in Eagle Ford is investigated. The simulation result shows that if the reservoir pressure is much higher than the bubble point pressure, the nanopore confinement effect will have a minimal impact on the recovery factor (RF) for both the depletion and the first few cycles of gas huff-n-puff. Geomechanics is found to be an influencing factor on RF but not always in a detrimental way, as enhanced rock compaction drive could offset the reduction of permeability in certain scenarios. Gas huff-n-puff would improve the RF of each component compared with the depletion. The heavy component would first have a higher recovery than the light component at the first few cycles of huff-n-puff, but its RF will be outpaced by the light component when the gas saturation in the matrix surpasses the critical gas saturation. Lastly, considering the nanopore confinement effects would slightly reduce the RF of the light component but increase the RF of the heavy component after huff-n-puff when combined with the critical gas saturation effect in the matrix.
This study presents a 3D multiphase, multicomponent simulator which is a practical tool for accurately modeling of primary depletion as well as gas injection IOR/EOR processes in unconventional oil reservoirs. This simulator is not only of great importance for assisting researchers to understand complex multiphase and multicomponent behaviors in tight oil production but also of great use for engineers to optimize gas injection parameters in field applications.
Yu, Xiangyu (Colorado School of Mines) | Winterfeld, Philip (Colorado School of Mines) | Wang, Shihao (Colorado School of Mines) | Wang, Cong (Colorado School of Mines) | Wang, Lei (Colorado School of Mines) | Wu, Yu-shu (Colorado School of Mines)
Geomechanics plays an essential role in fluid/heat flow by affecting hydraulic parameters. This influence could be amplified when fractures exist in the system because fracture aperture is highly sensitive to stresses. Coupled fluid/heat flow and geomechanics model is considerably important in simulating thermal-hydrologic-mechanical process, such as geothermal reservoir development. At the same time, due to the rock matrix shrinkage or expansion, thermal stress exerted on fracture surface remolds the aperture significantly and should be incorporated in modeling heat related process.
In this study, a coupled fluid/heat flow and geomechanics model, TOUGH2-THM, was developed based on the parallel framework of TOUGH2-CSM, with stress tensor components as primary variables. This modification is aiming on computing normal stresses on discrete fracture surface such that fracture related parameters can be fully coupled with geomechanical model. Embedded discrete fracture model was also improved to be compatible with the geomechanical coupling. Both of TOUGH2-THM and modified EDFM were validated for further application.
A geothermal reservoir simulation is conducted by the newly developed model, demonstrating the capability of this program to perform coupled modeling. It is also concluded that geomechanics and especially temperature alteration induced stress could affect fluid/heat flow in fracture and rock matrix. Thus, production efficiency could be impacted as well. The thermal stress generated by temperature reduction could enhance the fracture permeability in orders of magnitude. Various scenarios of injection temperature were modeled and compared. It can be observed that geothermal reservoir development is negatively influenced by geomechanical (and thermal) effect on fractures. The coupled model is helpful to improve the simulation accuracy.
Mou, Jianye (China University of Petroleum Beijing, State Key Laboratory of Petroleum Resources and Prospecting) | Yu, Xiaoshan (Sichuan-to-East Natural Gas Transmission Pipeline Branch Company of SINOPEC) | Wang, Lei (China University of Petroleum, Beijing) | Zhang, Shicheng (China University of Petroleum, Beijing) | Ma, Xinfang (China University of Petroleum, Beijing) | Lyu, Xinrun (China University of Petroleum, Beijing)
Jianye Mou, China University of Petroleum, Beijing, State Key Laboratory of Petroleum Resources and Prospecting; Xiaoshan Yu, Sichuan-to-East Natural Gas Transmission Pipeline Branch Company of SINOPEC; and Lei Wang, Shicheng Zhang, Xinfang Ma, and Xinrun Lyu, China University of Petroleum, Beijing Summary Natural fractures have significant influence on flow fields, thus affecting wormhole pattern in acidizing. First, statistical natural-fracture models are established using the Monte Carlo method. Second, a two-scale continuum wormhole model is established to simulate wormhole propagation with natural fractures. Finally, extensive numerical simulation is conducted to investigate wormhole behavior and the effect of the natural-fracture parameters on wormhole pattern. In addition, possible wormhole-penetration distance is discussed. Introduction Matrix acidizing in carbonates is a typical measure to remove formation damage caused by drilling, completion, and other operations. The wormholes created in acidizing penetrate the damaged zone, thereby removing the damage and stimulating the reservoir. Stimulation performance depends on wormhole pattern, which in turn is influenced by many factors such as acid properties, injection rate, formation properties, and natural fractures.
Pang, Zhanxi (China University of Petroleum, Beijing) | Wang, Lei (China University of Petroleum, Beijing) | Wu, Zhengbin (China University of Petroleum, Beijing) | Wang, Xue (China University of Petroleum, Beijing)
Zhanxi Pang, Lei Wang, Zhengbin Wu, and Xue Wang, China University of Petroleum, Beijing Summary Steam-assisted gravity drainage (SAGD) and steam and gas push (SAGP) are used commercially to recover bitumen from oil sands, but for thin heavy-oil reservoirs, the recovery is lower because of larger heat losses through caprock and poorer oil mobility under reservoir conditions. A new enhanced-oil-recovery (EOR) method, expanding-solvent SAGP (ES-SAGP), is introduced to develop thin heavy-oil reservoirs. In ES-SAGP, noncondensate gas and vaporizable solvent are injected with steam into the steam chamber during SAGD. We used a 3D physical simulation scale to research the effectiveness of ES-SAGP and to analyze the propagation mechanisms of the steam chamber during ES-SAGP. Under the same experimental conditions, we conducted a contrast analysis between SAGP and ES-SAGP to study the expanding characteristics of the steam chamber, the sweep efficiency of the steam chamber, and the ultimate oil recovery. The experimental results show that the steam chamber gradually becomes an ellipse shape during SAGP. However, during ES-SAGP, noncondensate gas and a vaporizable solvent gather at the reservoir top to decrease heat losses, and oil viscosity near the condensate layer of the steam chamber is largely decreased by hot steam and by solvent, making the boundary of the steam chamber vertical and gradually a similar, rectangular shape. As in SAGD, during ES-SAGP, the expansion mechanism of the steam chamber can be divided into three stages: the ascent stage, the horizontal-expansion stage, and the descent stage. In the ascent stage, the time needed is shorter during ES-SAGP than during SAGP. However, the other two stages take more time during nitrogen, solvent, and steam injection to enlarge the crosssectional area of the bottom of the steam chamber. For the conditions in our experiments, when the instantaneous oil/steam ratio is lower than 0.1, the corresponding oil recovery is 51.11%, which is 7.04% higher than in SAGP. Introduction SAGD is a method for ultraheavy-oil recovery that has already been industrialized and applied in oil fields (Butler 2001); however, there are a great number of problems associated with the process of SAGD. For instance, the effects of development gradually become worse because of the large heat loss and the high water cut in the later period of SAGD (Butler et al. 2000). Thus, an improved SAGD technology, called SAGP, has been introduced.
Wang, Lei (ExxonMobil Development Company) | Bailey, Jeffrey R. (ExxonMobil Development Company) | Rajagopalan, Srinivasan (ExxonMobil Corporate Strategic Research) | Ozekcin, Adnan (ExxonMobil Corporate Strategic Research) | Prim, Matthew (ExxonMobil Abu Dhabi Offshore Petroleum Company Limited)
Friction can be one of the major limiters in ultra-ERD (Extended-reach drilling) well completions. For some completion strings, friction running into the hole can limit the length of well to be drilled. Centralizers coated with novel Diamond-Like Carbon (DLC) coatings have been developed to provide operational advantages for these ultra-ERD applications. This paper will document the development, laboratory and field testing, and lessons learned from a project to evaluate the coated centralizer opportunity.
The project began with evaluation of currently available centralizers made of a hard material to support the thin low-friction coating layer. This led to selection of an inexpensive cast-iron centralizer that required machining and polishing prior to coating. Next we selected the coating chemistry, layer hierarchy and functionality, and interlayer properties, leveraging knowledge from an artificial lift application. Multiple coating compositions had previously been evaluated for friction and wear characteristics in Block-On-Ring laboratory tests.
Prototypes of the novel centralizer with selected coatings were tested against commercially-available centralizers in a lab environment, and field tests were subsequently conducted in two wells. These lab tests were conducted to assess the friction reduction potential of the coated centralizers. Tests were performed to measure the COF (Coefficient of Friction) of the coated centralizers against other types of uncoated tools made of cast iron, zinc alloy, pressed spring steel, and polymer under wet conditions in simulated cased and open hole. In these tests, the DLC coated centralizers yielded the lowest COF overall when compared to existing tools.
With promising lab results, the first field test was conducted in an onshore unconventional horizontal well with high doglegs. In this well, the data showed very low friction over a 580-m (1900-ft) open-hole interval. A second field trial was then conducted in an offshore ERD well in a liner running application. In this test, a stable low friction factor of 0.10 was observed over a 4000-m (13-kft) deviated section at 75°, measurably lower than the offset FF (Friction Factor) of 0.15. Both tests therefore demonstrated intervals of very low friction, however both experienced drag that might be the result of cuttings. To address this problem, a redesign has been prototyped based on a slicker centralizer profile. This new centralizer also requires less polishing and offers an inherently hard substrate that is beneficial to the coating durability.
These were the first field applications of DLC coated centralizers. While drilling, pipe can be rotated to release friction, but in completion operations this may not be possible. Although pipe can be air-filled to provide buoyancy, there are many examples of screens and perforated pipe that cannot be floated. In one effort to advance the industry capability to run casing strings in extended-reach wells, multilayered DLC coatings were successfully applied to cast-iron based centralizers and demonstrated in lab and field tests, and a prototype was developed to improve the centralizer profile.
Mou, Jianye (Shaodan Tao China University of Petroleum-Beijing) | Hui, Xuezhi (Seventh Oil Production Plant of Changqing Oilfield of CNPC) | Wang, Lei (China University of Petroleum-Beijing, State Key Laboratory of Petroleum Resources and Prospecting) | Zhang, Shicheng (China University of Petroleum-Beijing, State Key Laboratory of Petroleum Resources and Prospecting) | Ma, Xinfang (China University of Petroleum-Beijing, State Key Laboratory of Petroleum Resources and Prospecting)
Multi-stage acid fracturing of horizontal wells is a necessary and effective technology in developing tight carbonates. In open-hole horizontal wells in high-temperature, naturally fractured deep formations, segmentation with tools is of high risk and costly, even ineffective sometimes, so segmentation with diversion agents is alternative to tools and was pilot tested in some fields. The stimulation results were satisfactory, and pressure response feature was in accord with expectation. However, this technique has not been studied experimentally or numerically extensively yet.
In this study, we investigated tool-free multi-stage fracturing experimentally in open-hole horizontal wells with diversion agents. Firstly, we designed a multi-stage tri-axial fracturing system and experimental procedures to satisfy the requirements of diverted fracturing in horizontal wells. Next we conducted a series of experiments to investigate feasibility of multi-stage fracturing with diversion agents using natural carbonate outcrop cubic blocks with the size of 300*300*300mm. CT scanning was used to obtained detailed fracture geometry after experiment. Finally we analyzed the effect of diversion agent type, concentration, and injection procedure on diversion.
The experimental results show that multi-stage fractures perpendicular to the open-hole horizontal wells was created, which verifies the validity of the tool-free multi-stage fracturing of open-hole horizontal wells with diversion agents. Proper agents or combinations can effectively plug the fracture generated previously and generate pressure high enough to initiate another fracture. The breaking pressure or propagation pressure of second fracture was monitored higher than the one of the first fracture. Under experiment conditions, 1-3mm fiber or combination of fiber and particle (0.8-1.2mm) can effectively plug fractures and realize segmentation. Concentration of diversion agents tested ranges 0.4-1.6wt%. Injection procedure for two-stage fracturing was fracturing fluid + diversion fluid + fracturing fluid. The amount of diverter and open-hole length are the vital factor for the success of experiments.
This study newly designed a multi-stage tri-axial fracturing system and experimental procedures for the diverted fracturing. The finding verified the validity of the tool-free multi-stage fracturing of open-hole horizontal wells with diversion agents and provides fundamental for field treatment design.
Yuan, Xiyong (School of Geosciences, China University of Petroleum-East China, Qingdao, China) | Deng, Shaogui (School of Geosciences, China University of Petroleum-East China, Qingdao, China) | Wang, Lei (School of Geosciences, China University of Petroleum-East China, Qingdao, China) | Zhang, Pan (School of Geosciences, China University of Petroleum-East China, Qingdao, China)
Identification and characterization of fractures are critical to the exploration and production of tight reservoirs. This paper introduces a novel multi-array azimuthal resistivity laterolog logging method which can determine fracture position, aperture as well as the dipping angle and strike direction at the borehole level. We studied the responses with different fracture parameters, and numerical results show that amplitude difference among the array resistivity curves is dominated by fracture dipping angle, whereas the azimuthal resistivity are also controlled by fracture dipping direction. The azimuthal resistivity in fracture strike direction is low and the azimuthal resistivity in fracture dipping direction is high. Inclined fractures take on a sine-wave trend in azimuthal resistivity images, which indicates the attitude visually. Furthermore, this method can recognize high-angle fractures around borehole in a considerable distance. A simplified scaled-down experimental instrument was also designed to verify the accuracy of the method. Experimental test shows good consistency with that from numerical results, further indicating the accuracy and feasibility of the proposed method.
Presentation Date: Tuesday, October 16, 2018
Start Time: 1:50:00 PM
Location: 212A (Anaheim Convention Center)
Presentation Type: Oral
Mou, Jianye (China University of Petroleum Beijing, State Key Laboratory of Petroleum Resources and Prospecting) | Yu, Xiaoshan (Sichuan-to-East Natural Gas Transmission Pipeline Branch Company of SINOPEC) | Wang, Lei (China University of Petroleum Beijing) | Zhang, Shicheng (China University of Petroleum) | Ma, Xinfang (China University of Petroleum Beijing) | Lyu, Xinrun (China University of Petroleum Beijing)
Jianye Mou, China University of Petroleum, Beijing, State Key Laboratory of Petroleum Resources and Prospecting; Xiaoshan Yu, Sichuan-to-East Natural Gas Transmission Pipeline Branch Company of SINOPEC; and Lei Wang, Shicheng Zhang, Xinfang Ma, and Xinrun Lyu, China University of Petroleum, Beijing Summary Natural fractures have significant influence on flow fields, thus affecting wormhole pattern in acidizing. First, statistical natural-fracture models are established using the Monte Carlo method. Second, a two-scale continuum wormhole model is established to simulate wormhole propagation with natural fractures. Finally, extensive numerical simulation is conducted to investigate wormhole behavior and the effect of the natural-fracture parameters on wormhole pattern. In addition, possible wormhole-penetration distance is discussed. This study provides a theoretical basis for matrix-acidizing designs in naturally fractured carbonates. Introduction Matrix acidizing in carbonates is a typical measure to remove formation damage caused by drilling, completion, and other operations. The wormholes created in acidizing penetrate the damaged zone, thereby removing the damage and stimulating the reservoir.
He, Min (Installation Division, Offshore, Oil Engineering Co., Ltd.) | Wang, Alan M. (Installation Division, Offshore, Oil Engineering Co., Ltd.) | Li, Litao (Installation Division, Offshore, Oil Engineering Co., Ltd.) | Chen, Yining (DNV-GL Oil&Gas) | Li, Xin (Shanghai Jiao Tong University) | Wang, Lei (Shanghai Jiao Tong University)
This paper presents a comparative study of the numerical simulations and the field measurements for a 23,322Te large jacket launch into a water depth of 190.2 meters in South China Sea. The sensitivity simulations demonstrate that the friction coefficient between jacket launch cradles and barge launch skidways is the dominant factor in the jacket launch simulation. This domain factor plays the most important role in the jacket launch. It recommends that a friction coefficient ranging from 0.03 to 0.08 should be used in the sensitivity analysis of jacket launch in the future. This comparative study not only ensures the integrity of the large jacket and the launch barge during launch, especially at tipping, and a clear safe separation between launch cradles and rocker arms, but also benefits safe launch operations by calibrating the numerical modeling in the launch simulations of future jacket installations.
A comparative study has been conducted to investigate the launch simulation and field measurement of an 8-legged jacket launch into a water depth of 190.2m in South China Sea. The factored launch weight of Pan Yu 34-1 jacket is approximately 23,312Te with a total height of 203.5m. The world's second largest T-shaped launch barge “Hai Yang Shi You 229” was selected to launch this large jacket. Refer to Fig. 1 for the views of the PY34-1 jacket launch. The comparison of the jacket launch simulation and field measurement is used to calibrate the jacket launch simulation predicted by the computer software MOSES and also to study the uncertainty and inaccuracy of the T-shaped launch barge due to its shoulder effect of midbody transition.
Two independent sets of Inertial Navigation Systems (INS) and Global Positioning Systems (GPS) were installed on the two launch cradle legs to measure the trajectory motions and accelerations of the launch jacket, thus ensuring a 100% redundancy and a double check with each other. A third GPS system is also used to measure the motions and accelerations of the launch barge. In addition, optical fiber strain gauges were installed on both the rocker arms to monitor the reaction loads acting on the two rocker arms from initial launch, tipping, until separation. A parametric analysis of the jacket launch simulations was performed by varying the friction coefficients between launch cradles and launch skidbeams, the jacket weight, the offset of jacket center of gravity, the barge drag coefficients due to the T-shaped hull, etc. The comparison of the numerical findings and the field test results is then used to investigate the impact of the T-Shaped launch barge and other potential influence parameters, and therefore determining the dominant parameter of interest.
Vortex connections at surface are fundamental and prominent features in free surface vertical flows. Such connections are characterized by strong surface tension and air entrainment. In this paper, a primary objective is to understand the detailed mechanism of air entrainment induced by vortex structures. Direct numerical simulations (DNS) are performed for this problem. Horizontal vortex tube and vortex ring are defined as two canonical problems for laminar free surface vortex connection problems. Particularly, the vortex structure free-surface evolution and surface secondary vorticity which elucidate vortex connection and air entrainment process for both two canonical problems are investigated in detail. A key finding is that the entrainment process highly depends on Froude number (Fr) with the entrained air volume linearly proportional to Fr2.
Air-water mixture is induced by flowing water and air at free surface, which is common in daily life as well as many industries such as chemical, naval, and biological engineering. For example, in civil and environmental engineering, aeration cascades, used in sewage and water treatment plants, combine the effects of air entrainment and high turbulence intensity to enhance the mass transfer of volatile gases(Tryggvason et al., 2006). In naval engineering, the air entrainment induced by a fleeting ship contributes to the white water bubbly wake which persists over long distances leaving behand distinct acoustical and non-acoustical signatures.
Understanding the dynamics and mechanism of air entrainment is of critical engineering importance and the literature is extensive. From the mathematical point of view, the origin (governing equation) for multiphase flow is difficult (Tryggvason et al., 2011). The highly non-linear governing equation as well as the complex boundary condition make it even harder to resolve the issue. Experimental studies for air entrainment are also not easy. The entrained bubbles range widely in size. High resolutions are generally needed to resolve the bubbles in numerical simulations. However, due to the limitation of computational resources, reasonable resolutions are used in numerical simulations and only relatively large bubbles are resolved. So a detailed resolution of the entrainment mechanism and the resolution for all range of bubbles are needed.