Ming, Eryang (PetroChina Research Inst Petr Expl & Dev) | Li, Tao (PetroChina Research Inst Petr Expl & Dev) | Li, Yiliang (PetroChina Research Inst Petr Expl & Dev) | Pei, Xiaohan (PetroChina Research Inst Petr Expl & Dev) | Hao, Zhongxian (PetroChina Research Inst Petr Expl & Dev) | Guo, Tong (PetroChina Research Inst Petr Expl & Dev)
In recent years, the flexible coiled composite pipe (FCCP) has developed rapidly in China. Because of its merit about chemical inertness, it has been introduced to onshore oilfields to endurance some severe situations, such as serving as tubing in corrosive and waxy oil wells, as tubing in scaling water injection wells or as surface gathering pipelines, especially suitable for mountainous areas. This paper will introduce the development status of FCCP in different applications.
According to our research and development, for FCCP structure manufacture, there are two main technical routes in China, non-adhesive pipe and adhesive pipe. These two kinds of pipe meet the merits of FCCP, however, there are some differences in technical parameters. Obviously, non-adhesive pipe has smaller bending radius, but the integrity of adhesive pipe is better which is good for fitting installation. In this technical stage, the FCCP has been applied in surface gathering system, general water injection system and rodless artificial lift system.
For surface gathering system, this is the most mature application of this technology. It has been laid over 30,000 kilometers. Compared with steel pipe, the equipment of FCCP is simple and high laying efficiency. For general water injection system, the FCCP replaces steel pipe by high working efficiency and long endurance. It has been applied more than 80 wells. For rodless artificial lift system, there are almost 60 wells applied FCCP. It is the severest running condition for FCCP with high temperature, high wellbore pressure and high varies suspension force. This application reveals the advancement of FCCP by twining cables inside the pipe body and adding functions of real-time monitoring and heating. Two typical applications are serving as tubing in cold heavy oil production and acid gas corrosion oil well. The application of FCCP has made great progress. But there are several key issues that need to be resolved in the future research. First, there is lack of post evaluation of performance. Second, the limit of material working temperature shrinks the application scope. Third, the external pressure resistance is limited.
This paper shows the applications of flexible coiled composite pipe in onshore oilfields of China in the past 5 years, including a summary of technical experience, and proposing the goal of further research.
Gas hydrates has been widely believed to be able to revolutionize the energy supply for future, so far pilot offshore trials were completed by both China and Japan, yielding significant breakthrough and experience, while also exposing its vulnerable production system. In this paper, the production system of gas hydrates was studied comparatively based on offshore tests, the challenge of sand production and artificial lift were presented in detail, new technique aimed at enhancing the gas output in a safety manner was discussed. The results indicated that sand production was the primary threat to the sustainability of gas hydrates production, gravel packing and shape memory polymer were employed by Japan in the field tests but both yielded unsatisfied results, the strategy on this should be the combination of both prevention and governance which means to allow in sand of small size while keeping large sand out of the wellbore; artificial lift was the key in regulating the dissociation ratio of gas hydrates, usually the faster the ratio, the more risk of reservoir damage, the slower, the less water produced which led to high temperature in the ESP system, enhancedrecovery technique was an urgent task in consideration of low gas output, the focus should be on how to maximize the dissociation zone of gas hydrates while preserving the integrity of the reservoir, the current tactic was the deployment of slim wellbore according to the dissociation front of gas hydrates, sustaining the gas production while maintaining the integrity of reservoir, meanwhile wellhead group should be easily installed and retrieved. The experience and lessons of production system gained during the offshore gas hydrates extraction were reviewed in this paper, the results contributed to its solid performance in future, which could guarantee the commercialization people expected.
Liu, He (RIPED, CNPC) | Zhang, Shaolin (RIPED, CNPC) | Sun, Qiang (RIPED, CNPC) | Li, Tao (RIPED, CNPC) | Ming, Eryang (RIPED, CNPC) | Huang, Shouzhi (RIPED, CNPC) | Han, Weiye (RIPED, CNPC) | Chen, Qiang (RIPED, CNPC) | Li, Yiliang (RIPED, CNPC) | Pei, Xiaohan (RIPED, CNPC)
After long-term water-flooding, many of the matured fields in China have experienced changes in the physical properties of reservoirs. Moreover, the inefficient cycle of water flooding in the reservoirs is serious, and the heterogeneity of reservoirs causes difficulty to determine the distribution of remaining oil. It is impossible to reflect the real situation of the stratum only by simulation analysis with the numerical simulation software. To core in a specific location through coring technology and analyze the core can not only re-conduct a more accurate evaluation of the stratum, but also can modify relevant data of existing models to improve the simulation accuracy. But the current technology can’t conduct coring operations near wellbore and in deep parts.
Therefore, based on the ultra-short radius sidetracking technology, this paper aims to develop ultra-short radius flexible sealed coring technology to achieve coring outside the casing. Compared with the ultra-short radius sidetracking technology, the ultra-short radius flexible sealed coring technology has, in addition to the windowing, deflecting, and horizontal drilling tools, the core tools of this technology, that is, the flexible sealed coring tool. The tool is mainly composed of a flexible outer cylinder and a highly elastic titanium alloy inner cylinder. The flexible outer cylinder is connected by a multi-section of flexible units that can be bent up to 5°. And a special coring bit is connected to the front of the tool. The maximum length of the core taken in a single coring process is 1.1 meters; the core diameter is up to 40mm. By using this technology, the minimum horizontal distance of the core position and the borehole wall is 0.8 meter, and the maximum horizontal distance can be up to 100 meters.
At present, the technology has been successfully applied to more than 10 wells, and the average core recovery rate has reached 90%, which provides valuable data for the geological departments and is of great significance for re-developing matured fields.
This technology can obtain the core from outside of the casing and near wellbore, and offers a more accurate evaluation on changes of physical properties of the reservoirs, providing the basis for adjusting the subsequent water flooding development plans.
With the further development of natural gas, the quantity of gas well has been increasing year by yearin China, the demands for well completion and workover are growing. At present, more than 70% of gas wells are low yield and low pressurein China, in order to protect the reservoir and make the production stably, it's an urgent need to use snubbing technology for low pressure gas well.
Snubbing technology faces several challenges for low pressure gas well, such as high risk, complex downhole conditions, high cost, low operation efficiency, etc. High efficiency, low cost and low risk are crucial targets for gas well snubbing. To achieve this target, we developed a set of snubbing wellhead for low pressure gas well which operation pressure is less than 14MPa. Some key technologies are formed, such as airtight makeup and breakout device, gas sealing system, rotating slips etc. The unit can realize pipe tripping and rotating operation with high efficiency and low risk in low pressure gas well, it's composed of lifting system, gas sealing system, working BOP stacks, airtight makeup and breakout device, security BOP stacks. The main working principle is adopted liquid to seal gas, the gas sealing system is composed of two sets of annular preventers, and a length of liquid which has 3-4MPa pressure is sealed between them. When it comes to begin snubbing operation, the gas sealing system can realize effective sealing within the wellbore pressure and also achieve the purpose of tubing lubrication, the safety and reliability can be well guaranteed when it works with BOP stacks. The airtight makeup and breakout device is equipped between the working BOP stacks and security BOP stacks, cooperate with the rotating slips, tubing joints can be screwed on and off at the bottom of the snubbing wellhead when it meets special snubbing work conditions, such as no tubing plug or tubing leakage.
The pilot test of this technology is carried out in Jilin oilfield, operation cost is reduced about 50%, and it makes the production development more effectively and economically.
The annual demands of snubbing operation for low pressure gas wellare probably more than2000 wells each year in China, This technology has the advantages of high efficiency, low risk and low cost, the application prospectis broad.
There are a number of challenges existing in conventional slip-type liner hanger, such as undersealing annular of overlapping liner, limited high temperature resistant performance, et al. With the development and improvement of expandable tubular technology, expandable liner hanger (ELH) is developed to replace the current hanger and external packer completely, aiming at the shortcomings of the conventional liner hanger. ELH can isolate packer liner and the main casing, replace the conventional cement sealing way, and reduce the overlap length.
Here a new thermostable ELH was developed to apply in HT sidetracking well completion. The length of annular seal section of ELH is short but reliable, and maximum sealing pressure reaches 35 MPa. According to the requirements of the drilling process, tool string can be lifted, lowered, rotated and circulated to ensure extension liner string down to the bottom and improve the quality of liner cementing. The construction process is simple with low pressure, reliable operation and long service life after the production. The ELH has large bore size, larger than conventional casing under the hanger, in order to run in oil pump through the extension liner string. So the running in depth of pump is not affected by hanger diameter that can improve oil recovery ratio. The metal sealing is used in ELH for heavy oil thermal recovery wells, and it can be used under highest temperature of 300 C. This ELH tool string can fulfill tool setting and bottom sub salvage at one trip. The annular seal pressure of ELH is more than 35 MPa, construction pressure is 25 to 35 MPa, and suspension force is 600 kN.
This new ELH technology has been applied in HT sidetracking well completion in Liaohe oilfield. The hanger position is from 1491 m to 1493 m, inclination is 89 degree, the length of overlapping section in casing is 33 m, the length of sieve tube is 204 m, the length of blank casing is 55 m, and total length is 259 m. The running in depth of sieve tube guide shoe is 1753 m. Lift string suspending weight is 32 tons. ELH suspension was successful.
This paper provides a solution to HT sidetracking well completion using thermostable ELH technology. And the experience of operation process was shared in this case to be helpful for technology applications in similar situations.
Ming, Eryang (PetroChina Research Inst Petr Expl & Dev) | Li, Yiliang (PetroChina Research Inst Petr Expl & Dev) | Li, Tao (PetroChina Research Inst Petr Expl & Dev) | Huang, Shouzhi (PetroChina Research Inst Petr Expl & Dev)
The ultrashort radius lateral drilling technique has applied more than 20 wells in China, and it was reported that this technique increased the production of mature oil wells by 3 to 5 times in average. However, when the casing grade was relatively high, the flexible drilling tool was cut off by the sharp edge of open window. This paper will introduce a method to improve this technique.
By studying the failure case, there were two obvious defects for this drilling tool. First, the shell material was too soft. It was radially stripped of 2 to 3 mm. Second, the design of transmission fork was unreasonable. The cylindrical pins of transmission fork were placed from the outside of shell and were covered by welded discs. When the shell was stripped, pin was easy to drop off and causes disconnection. To find the essential cause, we deduce kinematics and dynamics analyzes, and redesign the structure of transmission fork. Test shows the performance of new tool is much better.
This paper introduces kinematics and dynamic to redesign the ultrashort radius lateral drilling tool, which improves the performance by principle. Though kinematics analyze, we found the rotational speed inhomogeneity might cause inefficient drilling depth, even sticking of tool in some extreme cases. Tough dynamic analyze, we found the additional torque caused by rotational speed inhomogeneity might cause the vibration of drilling tool, which may cause more serious problem. To solve these problems, the universal joint was design into constant velocity universal joint and the mounting position of transmission part was placed from inside to give enough margin for shell stripping off. After these work, the ultrashort radius lateral drilling tool has less vibration and provides continuous and stable torque. This method improves the efficiency and success rate of this technique.
This paper updates the design method of ultrashort radius lateral drilling technique, makes it much reliable and efficient. It will give the promise for the next generation technique, the ultrashort radius lateral coring technique.
Liu, He (Research Inst Petr Expl & Dev) | Ming, Eryang (Research Inst Petr Expl & Dev) | Han, Weiye (Research Inst Petr Expl & Dev) | Li, Tao (Research Inst Petr Expl & Dev) | Li, Yiliang (Research Inst Petr Expl & Dev) | Pei, Xiaohan (Research Inst Petr Expl & Dev) | Sun, Qiang (Research Inst Petr Expl & Dev) | Huang, Shouzhi (Research Inst Petr Expl & Dev)
Since the popularizing of snubbing technique in China, a number of new types of snubbing units appeared in oil fields. Without new industrial standards, it was difficult for users to choose the exactly suitable units to fit into their conditions. Consequently, most units were inefficient and accompanied high maintenance cost. It is urgent to draft a rational selection reference for solving above problems.
This paper introduces an evaluation method on varied versatile snubbing units except those special units, including classification, rationales, characteristics, advantages & disadvantages, and costs. Based on investigation, by comparing rationales and analyzing structure characteristics, the snubbing units can be classified into several types. Advantages & disadvantages provide the comparisons of mobility, integration, theoretical efficiency and well site requirements. The cost evaluation which is composed of acquisition cost, operation cost and maintenance cost provides an economic effectiveness ranking among different types. According to these five aspects' comparisons, the rated ranges of use are provided.
According to this evaluation method, snubbing units in China are divided into 2 types, separated type and independent type, and subdivided into 5 subtypes. Normal rig-assistant type and single hydraulic power rig-assistant type belong to separated type. Rig-less type, vehicle-mounted integration type and hydraulic energy-storing service rig type belong to independent type. Each subtype associates with specific rationale and structure characteristics, and it is easy to identify by users. Furthermore, each subtype has unique level of mobility, integration, theoretical efficiency and well site requirements, which means that users have more accurate specifications to choose ideal snubbing units for their certain conditions. What is more, there is a cost evaluation to balance their budgets or anticipations before purchasing. For example, in the northeast of China, the well depth is average and it is a plain area. According to this method, mobility should be the main consideration in all matters. Therefore, vehicle-mounted integration type is highly recommended to the users from that area. However, in the southwest of China, because of the mountains, separated type is better. This selection reference is very convenient and effective for Chinese users.
The research result in this paper helps users, mainly, producers and managers to acquaint snubbing units' situations in China and to take advantage of that for better work performance. It promotes standardization of snubbing industry and has formed a new industrial standard. In addition, this result potentially improves the rate of capacity utilization which is particularly beneficial to petroleum industry.
Liu, He (RIPED, CNPC) | Huang, Shouzhi (RIPED, CNPC) | Sun, Qiang (RIPED, CNPC) | Ming, Eryang (RIPED, CNPC) | Li, Tao (RIPED, CNPC) | Han, Weiye (RIPED, CNPC) | Chen, Qiang (RIPED, CNPC) | Li, Yiliang (RIPED, CNPC) | Pei, Xiaohan (RIPED, CNPC) | Zhang, Shaolin (RIPED, CNPC)
Numbers of oil fields in China had entered high water cut stage. The inefficiency circulation happened frequently during water flooding of these oil fields because of seriously intraformational heterogeneity in thick reservoir. Based on oilfield development dynamic data, it indicated that the problems of inefficiency fluid injection and futility circulation could not be solved in vertical well exploitation, no matter using water flood or chemical flood. There was a certain thickness of unexploited or low flushing efficiency oil remained on the top of thick reservoir. The traditional lateral drilling techniques could not be applied in short radius within 5 1/2 inches to 7 inches casing which were regular casing sizes of injection well in these oil fields. To exploit remained oil, the recent method to increase flow conductivity was hydraulic jet technology. But it had several disadvantages, like small aperture diameter, short drilling distance, inaccuracy orientation and limited flow conductivity.
This paper introduces an ultrashort radius lateral drilling technique (URLD) which provides an efficient method to increase production by drilling into the target reservoir to build a flow channel between unexploited reservoir and wellbore. The ultrashort radius lateral drilling technique includes flexible lateral drilling tool, deflecting tool, directional tool, etc. The flexible lateral drilling tool, which is the key in URLD technique, is consisted of several flexible nipples in the length of 15 cm. It is connected by double offset universal joint between adjacent flexible nipples. The movable angle between adjacent flexible nipples is 4-6 degree. And a PDC drill bit is connected in front end of tool. The URLD technique can realize lateral drilling within 5 1/2 inches to 7 inches casing. It can be applied to target reservoir thicker than 2 m. The drilling track is controllable. Target error is within ±1 %. Minimum deflecting radius is 1.8 m. The drilling hole diameter is 114 mm. The length of lateral drilling is more than 100m in 5 1/2 inches casing and 200 m in 7 inches casing.
The URLD technique has applied in more than 20 wells in China, and barels oil per day increases by 3 to 5 times in average. The URLD technique provides a solution to exploit remained oil after long term water flooding, and increases the production of mature oil field in economical way.
Details of estimating these approximate PPDs can be found in Padhi and Mallick (2014) and Li and Mallick (2015). The dashed curves, shown in Figure 3 denote the search windows used for estimation each model parameter. Notice from Figure 3 that the peaks of these estimated PPDs were connected to obtain an estimate for each model parameter. Also notice although we used a wide window for estimating each model parameter, the estimated PPD functions are very wellconstrained. The sliding window inversion allowed good constraints on the model parameter estimates from shallow to deep, which, in turn, is clearly reflected in these PPD estimates. Figure 2: An example of the 3-component VSP data used in this inversion study.
We develop a 3D Finite Element Method for solving the elastodynamic equation with high-order absorbing boundary conditions based on Higdon’s radiation boundary conditions using special potential functions. In the exterior of the domain, the unbounded elastic medium is assumed to be homogeneous and isotropic. This boundary condition is incorporated with no limitation on its order. A standard finite element discretization using second-order tetrahedral elements is performed in space, which is convenient for the elastic anisotropic problems; and a Newmark-type scheme is used for time marching. No numerical instability is observed for the simulation times of interest. This seismic forward modeling scheme could be applied to model full anisotropic 3D structures and be potentially applied to a full anisotropic inversion scheme.
With increasing interests in the unconventional and fractured reservoirs, characterizing the subsurface for azimuthal anisotropy has become important. Prestack waveform inversion (PWI) of multicomponent seismic reflection data has been shown to be an effective tool for anisotropic subsurface characterization (Padhi and Mallick, 2013, 2014; Li and Mallick, 2015). But these PWI schemes use an analytical forward modeling method which restricts their application to simple subsurface geometries. Forward modeling based on numerical methods on the other hand achieve the required accuracy while allowing arbitrary space dependence of the material properties. In this work we consider the finite-element method (FEM) for the solution of 3D full elastic wave equations. The main advantage of the FEM approach is its versatility to fit the characteristics of each problem; in particular, it allows the use of non-uniform grids, having elements with varying characteristic size, geometry and order of approximation (Serón et al., 1990). However, due to the finite computational domain, one of the persistent problems in the numerical solution of wave equations is the artificial reflections from model boundaries. Here we derive a 3D absorbing boundary condition (ABC) based on the methodology originally proposed by Hagstrom and Warburton (2004). The order of the ABC determines its accuracy and can be arbitrarily high and thus it is convenient for seismic modeling. In this paper we first introduce 3D elastodynamic equations in displacementstress formulations and propose a strong form of ABC.