Liu, Yongsheng (China University of Petroleum, Beijing) | Gao, Deli (China University of Petroleum, Beijing) | Li, Xin (China University of Petroleum, Beijing) | Qin, Xing (China University of Petroleum, Beijing) | Li, He (China University of Petroleum, Beijing) | Liu, Hang (Yibin Natural Gas Development Company Limited)
Jet comminuting technology has proved to be an effective means of solid particle pulverization, and current research attempts to introduce it for drilling work to reduce cuttings size, because smaller cuttings are easy to circulate out of the bottom, thus can effectively prevent the formation of cuttings bed, especially in horizontal drilling. In this paper, the feasibility of cuttings’ comminution by jet is studied by means of numerical simulation with secondary development. The coupling analysis methods—including the computational-fluid-dynamics/discrete-element-model (CFD/DEM) modeling for the interaction between fluid and cuttings and the particle replacement and bonding modeling for cuttings breakage—are used to characterize the jet comminuting process of cuttings. Input parameters of simulation are reliable and verified by uniaxial compression tests. Case studies presented here indicate that cuttings can be considerably accelerated by 20 to 30 m/s through the throat, which provides a good effective speed for the cuttings. After being accelerated by the fluid and crushed with the target, the vast majority of cuttings results in smaller debris. Also, increasing the inlet speed affects the crushing efficiency. The inclination of the target at near 65 shows good results. This paper proposes a new perspective to introduce the jet comminuting technique for drilling operations, and its findings could help in guiding engineering design in the future.
Tan, Leichuan (China University of Petroleum-Beijing) | Gao, Deli (China University of Petroleum-Beijing) | Li, Ningjing (China Petroleum Pipeline Engineering Corporation) | Ren, Shaoran (China University of Petroleum-East China) | Li, Xin (China University of Petroleum-Beijing) | Liu, Yongsheng (China University of Petroleum-Beijing) | Wang, Zhengxu (China University of Petroleum-Beijing) | Chen, Xuyue (China University of Petroleum-Beijing) | Gao, Chao (University of Texas at Austin)
Due to the high shale content and low permeability in shaly unconsolidated sandstone (SUS) reservoirs, the crude recovery rate can be very low. Fracturing is the key technology for developing such reservoirs. Thus, whether smooth fractures can be formed or not is important to improve production and to maximize economic benefit. In the study, a SUS model based on PFC discrete element method (DEM) is established firstly. Through the stress-strain curve fitting of the uniaxial pressure experiment, the microcosmic parameters are obtained. Meanwhile, the hydraulic fracturing PFC model of SUS is built by considering the fluid-solid coupling theory. The simulation shows that natural fractures can be connected by fracturing fluid to form branching fractures in hydraulic fracturing, but the main fracture still extends along the direction vertical to the minor principal stress. The crustal stress field can obviously affect the shape of hydraulic fractures in SUS. The smaller the stress difference is, the more fractures have the tendency to form disorderly fracture zones; with the increase of stress difference, fractures become more and more straight. It is also found that the stress chain direction is obvious after loading stress field to SUS, but the uneven distribution of stress is serious. The phenomenon leads to the shear stress emergence in the process of fractures expansion, making fractures direction more easily turn to the branches and produce fracture zones. Combining PFC microcosmic parameters and fracturing curves, it is believed that the normal and shear stiffness of sandstone particles are larger than those of shaly ones. To achieve the same stress, shaly ones need larger displacement, requiring more hold pressure time. Besides, the Poisson’s ratio and strong plasticity both are related to SUS shear failure. The study results can provide a basis for optimizing the design of hydraulic fracturing in SUS reservoirs.
The newest round of oil &; gas resources evaluation in China indicates that shaly unconsolidated sandstone (SUS) reservoirs are widely distributed and equipped with large reserves, occupying a foremost position in the whole oil &; gas exploitation and production. How to develop efficiently and rationally this type of oil &; gas reservoir has become one of the essential growth points is China’s relevant industry, which can be of great significance to improve the output and reduce production cost.
Gu, Yue (China University of Petroleum, Beijing) | Gao, Deli (China University of Petroleum, Beijing) | Yang, Jin (China University of Petroleum, Beijing) | Wang, Zhiyue (China University of Petroleum, Beijing) | Li, Xin (China University of Petroleum, Beijing) | Tan, Leichuan (China University of Petroleum, Beijing)
Shale gas in the mountain area is exploited in well factory mode. Learning effect due to well factory mode significantly affect the drilling cost, which has a powerful effect on platform location. The learning index, which is quantitative assessment of learning effect in the process of shale gas exploitment, is made by adjusted cosine similarity in this paper. The learning index, of which data comes from adjacent well, takes drilling cost, the well length and drilling time into account. The platform location optimization model, which considers learning effect, maximum number of wells one platform allowed and well trajectory, is established. The genetic algorithm is applied to solve the optimization model and the genetic operator is improved base on shale gas exploitation in mountain area. All the calculation procedure of genetic algorithm is performed in this work. The case study indicates that the optimization model can reduce the platform amount in a given area and increase the well amount one platform drills, namely, reduce the drilling cost by optimizing the platform location. The study demonstrates that the platform location optimization model established in this paper can both effectively quantify learning effect due to the well factory mode drilling in mountain area and decrease the drilling cost.
Li, Xin (Zhenhua Oil Company Research Center) | Huang, Haiping (Zhenhua Oil Company Research Center) | Lu, Hao (State Key Laboratory of Oil and Gas Reservoir Geology and Exploration, Southwest Petroleum University)
Knowledge of permeability is critical for developing an effective reservoir description. The accuracy of petrophysical models of permeability from conventional methods is relatively low. In this paper, the concept of flow units is used to evaluate formation permeability for a carbonate reservoir located in Iraq. Based on comprehensive analysis of core and well log data, flow units are established and subsequently are used to model permeability among several flow units. Correlation between porosity and permeability in each flow unit improves significantly, resulting in the establishment of a permeability model for each unit. Comparison of calculated permeability and core results indicates a highly accurate permeability model. Mercury injection data including Pc10, Rc50 and pore throat size, integrated with thin section observations, are also used to evaluate the physical properties of three distinct flow units. Permeability profiles are generated for each flow unit using well log data agree with core data. This agreement illustrates the potential and applicability of the flow unit method in complicated carbonate reservoirs.
Presentation Date: Wednesday, October 17, 2018
Start Time: 8:30:00 AM
Location: 209A (Anaheim Convention Center)
Presentation Type: Oral
Zhang, Yonghao (Department of Geology, Northwest University) | Ma, Jinfeng (China Petroleum Logging Co., Ltd) | Li, Xin (Department of Geology, Northwest University) | Zhu, Hanbing (China Petroleum Logging Co., Ltd) | Jiang, Liming (China Petroleum Logging Co., Ltd) | Li, Bing (China Petroleum Logging Co., Ltd) | Wang, Fei (China Petroleum Logging Co., Ltd)
Based on the analysis on the existing brittleness index and fracability evaluation methods of shale, the concept of fracability index (
Presentation Date: Wednesday, October 17, 2018
Start Time: 9:20:00 AM
Location: Poster Station 16
Presentation Type: Poster
Hong, Yugang (Chengdu Research Center of Zhenhua Oil) | Lu, Lize (Chengdu Research Center of Zhenhua Oil) | Abousleiman, Younane (University of Oklahoma) | Wang, Hehua (Chengdu Research Center of Zhenhua Oil) | Li, Xin (Chengdu Research Center of Zhenhua Oil) | Jiang, Liping (Chengdu Research Center of Zhenhua Oil) | Yang, Tao (Chengdu Research Center of Zhenhua Oil)
High permeability zones are critical to petroleum development of carbonate rock reservoirs. Prediction and description of high permeability zones is a big challenge between wells and outside well control area. Seismic attribute technology can extract information from seismic data that is otherwise hidden in the data and which will enhance the use and value of geophysics in the area of reservoir prediction and characterization. However, the weak relationship between each single attribute and reservoir features might be drowned out by noise or other information. Multi-attribute analysis such as Principle Component Analysis (PCA) and data fusion is becoming more popular for their advantage of integration and comprehension. PCA fusion is a useful tool to help to lower the dimensions of data without losing too much information and allow the data be understood easier. The component number of PCA is decided by the cumulative contribution larger than 0.85. The recomposed seismic attribute by PCA fusion comes from the selected primary components weighted by the ratios of the eigenvalue and the total eigenvalues. This new seismic attribute has been proved in Ahdeb oilfield that it has great consistency with the high permeability zone predicted by well logging data, and the high yield wells are mostly distributed in the zone. Risk could be significantly lowered when deploying new wells with this new seismic attribute.
Presentation Date: Monday, October 15, 2018
Start Time: 1:50:00 PM
Location: Poster Station 1
Presentation Type: Poster
ABSTRACT: During the process of horizontal extended-reach drilling (ERD), there are many different drilling operating conditions, including drilling with mud circulation, tripping in and tripping out, etc. In any operating condition, the too large or too small borehole pressure will pose a huge threat to the wellbore stability. Predicting the well's maximum measured depth (MMD) for only one drilling operation condition is not necessarily a guarantee for the safety of all drilling operations. It is necessary to predict the MMD for all drilling operations. In this study, considering ten different drilling operating conditions, a prediction model of horizontal ERW's MMD is established based on the dynamic pressure balance of bottom hole, and the predicted MMD mainly depends on annular pressure losses and the mud weight window (MWW). Furthermore, the effects of the model's parameters on these MMDs are also analyzed. The study shows some MMDs are related to the fracture pressure, namely the upper limit of MWW; while other MMDs are dependent on the collapse pressure, namely the lower limit of MWW. The minimum of these MMDs can be taken as the final MMD of the horizontal ERW. This work provides a practical tool for predicting the MMD of horizontal ERW and also provides theoretical guidance for ensuring the safety of all drilling operations.
The extended-reach well (ERW) plays a more and more important role in the exploration and development of oil and gas, especially in the development of shale gas and offshore drilling (Talkington et al., 1998; Martins et al., 2001; Wang et al., 2013; Wang et al., 2015; Wu, 2015). The world records of ERW's MMD are constantly created (Sonowal et al., 2009; Walker, 2012; Gupta et al., 2014). The theory of extended-reach limit based on fracture pressure theory can predict the maximum measured depth (MMD) of the ERW from the perspective of wellbore stability. The so called extended- reach limit based on fracture pressure is the ERW’ s MMD when the drilled formation is fractured. Gao et al. (2009) first proposed the theory of extended-reach limit based on fracture pressure and established the corresponding mathematical model. In 2016, some researchers further developed the theory, they applied the theory to the shale formations and offshore drilling, and the mud weight window (MWW) was also modified by the theory (Li et al., 2016a, b, c, d). The analysis results show that both the extended-reach limit based on fracture pressure and the horizontal-section limit of the horizontal ERW are determined by the bottom hole pressure and the fracture pressure of the drilled formation. Accurate prediction of ERW’MMD plays an important role in avoiding drilling hazards.
Deng, Qiao (China University of Petroleum) | Zhang, Hui (China University of Petroleum) | Li, Jun (China University of Petroleum) | Wang, Hao (China University of Petroleum) | Cai, Zhixiang (China University of Petroleum) | Tan, Tianyi (China University of Petroleum) | Li, Xin (China University of Petroleum) | Hou, Xuejun (Chongqing University of Science & Technology)
ABSTRACT: A number of models for estimating oil well perforation depths have been proposed by different scholars. However, earlier derived models have not accommodated a wide range of factors that affect the impact load of perforation, such as number of perforating charge, single charge, formation pressure, wellbore pressure and tubing length.
According to the classical Bernoulli's theorem, a model for estimating penetration length under different perforation conditions has been established and it contains an unknown function, which is used to calculate the initial pressure of the jet. In order to get the expression of the unknown function, a mathematical model based on numerical simulation results has been fitted, which can evaluate the sensitivity of the peak pressure on the perforating gun to changes under different conditions of perforation. The complete calculating model is finally created. The results of case study show that the predicted pressure by the model is accurate, within 10% of measured values by a pressure sensor installed at the bottom of the perforating gun during a well completion job.
This study proposed a novel method for the determination of the penetration length, which has important significance to provide guidance for the design of the perforating operations.
During past few decades, shaped charge jet perforation has been most widely used in the development of oil and gas reserves, the objective of which is to create tunnels between the formation and the wellbore that can efficiently transport hydrocarbons. The penetration depth of perforation is the most basic data for evaluating the productivity of oil and gas, which has been studied by a number of scholars.
The effects of formation stress on shaped-charge penetration and perforated-target flow performance have been studied by test (Saucier R J. 1978). On the basis of this previous study, the formula of shaped-charge penetration of rock under formation stress has been established (Halleck P M. et al. 1988). A model takes into account change in density of jet as it stretches during penetration while maintaining a constant diameter has been presented (Walters et al.1989). According to the logging data, the maximum and minimum perforating depths are figured out after the space between the perforating gun and the casing correction (Sun et al. 2004). The equivalent method to calculate jet perforation penetration length and hand-hole size of casing has been proposed (He et al. 2008). Actual perforation tests have been done with different shaped charges, rock cores and pressure system conditions according to API standard inspection equipment. The results show that the corresponding relationships between penetration and the dose, rock strength, porosity, acoustic velocity and effective stress are obvious (Li et al. 2010). The intent of this study is to develop a new mathematical model that can extend the scope of previous models and provide room for factors like target strength, explosive load, gun-to-casing clearance, effective impact area of jet/bullet, and velocity of perforator already known to affect perforation gun performance (F.H. Boukadi et al. 2010). In this study the perforation job is simulated numerically using PFC2D which is a 2D DEM code to evaluate the length of perforation tunnel (LPT) and the extent of damaged zone (EDZ) (Nabipour, A. et al. 2010). In order to study penetration capability of shaped charge jet penetrating into a soil /concrete target，the response characteristics of the soil /concrete target under shaped charge jet penetration were analyzed (Xiao et al. 2013). Based on the characteristics of deep sandstone under complex geostress, the influence of complex geostress on penetration depth of shaped charge into sandstone was analyzed，and a prediction formula of penetration depth under complex geostress was developed (Li et al. 2017).
Tan, Leichuan (China University of Petroleum) | Li, Ningjing (China Petroleum Pipeline Engineering Corporation) | Gao, Deli (China University of Petroleum) | Ren, Shaoran (China University of Petroleum) | Li, Xin (China University of Petroleum) | Liu, Yongsheng (China University of Petroleum) | Li, Wenlong (China University of Petroleum) | Gu, Yue (China University of Petroleum)
ABSTRACT: Complex fracture morphology may form in the hydraulic fracturing of high-rank coal rock resulting in poor coalbed methane (CBM) yield. This paper proposes a numerical simulation model which reveals the causes of poor hydraulic fracturing effect in Liulin block. Hydraulic fracturing experiments on eight coal samples collected from the target block were also conducted. Taken together, the results are used to establish three types of proppant-filling calculating models and fracturing construction curves which accurately show effective fracture lengths and yields. The results of this case study show that: (a) effective fracture length is the key factor affecting the CBM yield in the target block; (b) the CBM reservoir with high-rank coal rock readily forms complicated fractures, which does not allow for the proppant to fill into the designed position; (c) the model returns effective fracture length predictions within 9% of measured values by microseismic monitoring in the target block. This paper may provide theoretical guidance for the optimization of CBM reservoir hydraulic fracturing operations with high-rank coal rock.
Unconventional natural gas resources, particularly coal bed methane (CBM), have seen increasingly widespread development prospects in the energy structure of the 21st century. The CBM revolution in North America has been wildly successful as-evidenced by years of high yield. Although the Chinese CBM industry has rapidly expanded over the past several decades, its overall yields are still at a relatively lower level. The CBM of Liulin block, which is representative of the Ordos Basin, has typical characteristics of high-rank coal rock and thus very significant research value. Hydraulic fracturing has been widely applied in CBM as an important stimulation measure for enhancing gas production, but have been less successful in Liulin block.
Compared to conventional reservoirs, coal rock features a natural fracture, developed cleat, low Young’s modulus, and high Poisson’s ratio. The key to fracturing design and production evaluation is to recognize the fracture morphology in high-rank coal rock correctly.
Hubbert and Willis, 1957 proposed the first calculation formula for reservoir fracture pressure. Huang, 1981 studied the fracturing conditions and controlling factors of fracture extension, arguing that fracture formation mainly depends on the stress state of the wellbore; the factors influencing the stress state include crustal stress, pore pressure, borehole liquid pressure, and the mechanical and physical properties of percolation flow. Veatch, 1983 investigated the relationship between fracture extension and crustal stress in coal rock reservoirs; Krajcinovic, 1989 focused on constitutive equations of rock brittle materials and built corresponding models by applying the theory of thermodynamics.
Wang, Wenhua (Dalian University of Technology) | Wang, Bin (Powerchina Huadong Engineering Corporation Limited) | Zhang, Jie (Powerchina Huadong Engineering Corporation Limited) | Li, Xin (Dalian University of Technology)
ABSTRACT: The governing equation of motion of offshore wind turbine (OWT) under aerodynamic, hydrodynamic and seismic loads is derived based on blade element momentum theory (BEM), Morison equations and fundamental theories of structural dynamics. Then, a seismic analysis module is developed for the coupled analysis of a bottom fixed OWT under seismic, wind and wave loads according to the derived governing equation. An integrated bottom fixed OWT is presented referred to the NREL 5MW baseline wind turbine and a practical multi-pile offshore wind turbine in China. Dynamic characteristics and structural responses of the integrated OWT under earthquakes are analyzed by using the updated fully coupled analysis model. Then, the influence of the coupling effects of environmental load conditions on the structural responses can be found. Furthermore, the influence of seismic excitations in S-S direction for an operating OWT is investigated, it shows that the structure may confront with comparable responses in F-A and S-S direction simultaneously under such load conditions.
For the coastal and offshore regions in China, such as Bohai Bay and East China Sea, earthquakes may be the potential hazards in the planning of coastal offshore wind farms.
Prowell et al (2014) performed a utility scaled model test of a 65kW onshore wind turbine, then the dynamic characteristics under earthquakes and the influence of operating states on the structural responses are studied. Meanwhile, the aerodynamic damping effects should not be neglected in the seismic analysis of wind turbine. Valamanesh et al (2014), Salzmann et al (2005), Kühn et al (2001), Tempel et al (2000) and Male et al (2013) derived theoretical equations for the evaluation of aerodynamic damping ratios based on BEM and theories of structural dynamics. Valamanesh et al (2014) pointed out the variation of aerodynamic damping is closely related to the direction of the inflow wind, so the equations for the fore-aft (F-A) and side-side (S-S) direction are recommended, respectively. Devriendt et al (2013) and Shirzadeh et al (2013) determined the damping ratio of a monopile offshore wind turbine in F-A and S-S direction based on the actual measured data of the OWT, which involving the influence of structural damping, soil damping, hydrodynamic and aerodynamic damping.