Shi, Xiaoyan (CNPC Engineering Technology R&D Co. Ltd) | Zhou, Yingcao (CNPC Engineering Technology R&D Co. Ltd) | Zhao, Qing (CNPC Engineering Technology R&D Co. Ltd) | Jiang, Hongwei (CNPC Engineering Technology R&D Co. Ltd) | Zhao, Liping (CNPC Engineering Technology R&D Co. Ltd) | Liu, Yong (Petro China Tarim Oilfield Company) | Yang, Guang (CNPC Engineering Technology R&D Co. Ltd)
Influx and loss are the two most common downhole complexities. They not only cause the reservoir damage, increase the exploration cost, reduce the drilling efficiency; but also induce major malignancy. Therefore accurate and early detection of influx and loss during drilling is of great significance. Traditional influx and loss detection methods have the shortcoming of monitoring time lagging and high costs. As the rapid development of artificial intelligence techniques, researchers start to detect influx and loss using artificial intelligence method. This work adopted two machine learning algorithms(Random forests and Support vector machine) according to their characteristics to detect influx and loss during drilling in real-time. The detection methods includes four steps: 1) Generating raw influx/loss raw data set by combining real-time drilling data and drilling history data; 2) Pre-processing raw data set to obtain training data set; 3) Training classification model of random forests and SVM by training data set and algorithms; 4) Predicting influx/loss by the trained model according to the new real-time data. The case study shows that influx and loss can be detected accurately in early stage by both random forests method and SVM method after proper pre-processing the raw data and optimizing algorithm parameters. The detection accuracy of the sample data from four wells exceeds 90%. This work demonstrate a new way to detect influx and loss by utilizing huge drilling data and machine-learning algorithms, and the detection results are satisfying.
Zhang, Jian (State Key Laboratory of Offshore Oil Exploitation, CNOOC Research Institute Co., Ltd.) | Wang, Shanshan (State Key Laboratory of Offshore Oil Exploitation, CNOOC Research Institute Co., Ltd.) | Zhu, Yuejun (State Key Laboratory of Offshore Oil Exploitation, CNOOC Research Institute Co., Ltd.) | Yang, Guang (State Key Laboratory of Offshore Oil Exploitation, CNOOC Research Institute Co., Ltd.) | Kang, Xiaodong (State Key Laboratory of Offshore Oil Exploitation, CNOOC Research Institute Co., Ltd.) | Wang, Xudong (State Key Laboratory of Offshore Oil Exploitation, CNOOC Research Institute Co., Ltd.) | Zhao, Wensen (State Key Laboratory of Offshore Oil Exploitation, CNOOC Research Institute Co., Ltd.)
To effectively develop heavy oil with apparent viscosity above 150 mPa·s in-situ, a heavy oil activator was designed and applied in the field, which can efficiently increase the viscosity of aqueous phase and the mobility of oil phase. The wettability, interfacial properties and the microscopic dispersion of oil with activator were measured using the contact angle meter and laser scanning confocal microscopy. Experimental results showed that the contact angle between activator and heavy oil was 34.67° and the oil-water interfacial tension could be reduced to 0.1 mN/m by adding activator. Furthermore, it was clearly observed that the crude oil was uniformly dispersed into small drops. For the hybrid system consisting of 660 mPa's crude oil and 1000 mg/L activator with a mixed ratio of 1:1 by volume, the flowing time measured by kinematic viscometers was reduced to 8 s compared with 340 s of single oil system. By adopting the activator flooding, laboratory experimental studies showed the recovery of heavy oil could be enhanced by 14.3% on the basis of water flooding. The change of oil-water front and distribution of saturation field confirmed that the activator had the ability to disperse heavy oil and improve the micro-displacement efficiency, and the contribution rate accounted for about 28% of the total recovery. This obvious effect has been successfully achieved in pilot test of both S Oilfield and D Oilfield. By applying activator huff and puff in S Oilfield for 14months, the total incremental oil reached 44,952 bbl tons. And using activator of 800 mg/L to exploit heavy oil with viscosity of 1170 mPa·s in-situ at 35 °C. After 3 years of injection, the cumulative incremental oil of D oilfield was larger than 120,000 bbl, which means that each ton of activator can ramp up production of 660 barrels oil.
Composite propeller is found to have the characteristics of weight light, hydrodynamic performance improvement and noise reduction. In order to investigate its fluid-structure hydroelastic performance, potential based boundary element method (BEM) is coupled with finite element method (FEM) for the hydrodynamic analysis of composite propeller. The calculated thrust and torque present good agreement with the experimental hydrodynamic force. A series of comparative experiments in cavitation tunnel are conducted to research hydroelastic characteristics of composite propeller compared to metal propeller, including hydrodynamic performance test, hydrodynamic decline test, cavitation inception test and cavitation observation test. The “transition point” of the open water curve is discovered, at which the attack angle’s decrease balances the deformation to equal composite propeller and metal propeller. The composite propeller’s cavitation inception is later and cavitation area is smaller than metal propeller. The tests above all show that the hydroelastic self-adaptive characteristic gives composite propeller better hydrodynamic and cavitation performance than metal propeller.
Along with the development of propellers, composite propeller comes to be taken seriously due to its advantage of lightweight, higher efficiency, erosion or cavitation damage resistant, fatigue improvement, life cycle cost decrease and good acoustic damping characteristics. The fluid-structure interaction (FSI) hydroelastic effect is caused by the application of composite materials. The characteristics of lightweight and flexible change the hydrodynamic and structural performance, especially when anisotropic fiber ply optimized. A great deal of work begins by Young (2007, 2008) using potential-based boundary element method coupled with finite element method for the time-dependent hydroelastic analysis of cavitating propulsors and flexible composite marine propellers. The numerical method was invented to investigate moving cavity boundaries and fluctuating pressures, dynamic blade deformations and stresses(Young2008). Then the self-adaptive composite propellers occurred (Young2010). Some further research on the effects of material anisotropy and added mass on the free vibration response of rectangular cantilevered composite plates/beams was conducted (Young2013), results showed that the wet mode natural frequencies of the composite plate were 50–70% lower than dry mode due to large added mass effects, which varied considerably with material orientation then affected the mode shapes and fluid inertial loads.
Shi, Xiaoyan (CNPC Drilling Engineering and Technology Research Institute) | Zhou, Yingcao (CNPC Drilling Engineering and Technology Research Institute) | Song, Peng (CNPC Drilling Engineering and Technology Research Institute) | Zhao, Qing (CNPC Drilling Engineering and Technology Research Institute) | Jiang, Hongwei (CNPC Drilling Engineering and Technology Research Institute) | Huo, Zongqiang (CNPC Drilling Engineering and Technology Research Institute) | Yang, Guang (CNPC Drilling Engineering and Technology Research Institute) | Zhai, Xiaoqiang (CNPC Drilling Engineering and Technology Research Institute)
As the rapid development of drilling techniques and data acquiring techniques, more and more drilling data are available. Storing, managing and effective using of these massive data are crucial to optimized drilling engineering design and strategic decision. This article is to research and design an integrated drilling database, and then further explore the innovative usage of the available drilling data. Based on the detail analysis of drilling database requirement, this article researched and designed drilling database by three phases: conceptual design, logical design and physical design. In the conceptual stage, the requirements of drilling design data, real-time drilling data and drilling construction data are extracted and analyzed, then E-R model is constructed. In the logical design stage, data tables and table relationship are designed and refined based on the E-R model. In the physical design stage, physical structure is selected for the logical data model to satisfy the application requirement. The designed drilling database is targeted data storage and management basis for drilling engineering design and craft software, real-time drilling software and drilling history management software; it conforms to drilling business process, contains comprehensive and detailed content and has high performance and refined data table structure. The construction of unified drilling database enables the efficient storage of mass drilling data and further data mining and analysis of drilling information. This work further researched the algorithms of automatic drilling engineering design, especially for automatic wellbore geometry design, based on the available data in the database. This article introduced a systematic method to design an integrated drilling database, which supports design data, real-time data and drilling management data. It also proposed an innovative way of drilling engineering design: automated drilling engineering design based on the data in the integrated drilling database and pre-installed rules.
Xiong, Lingzhi (Shanghai Jiao Tong University) | Lu, Haining (Shanghai Jiao Tong University) | Yang, Jianming (Shanghai Jiao Tong University) | Zhang, Wei (Offshore Oil Engineering Co., Ltd, Engineering Company) | Yang, Guang (Offshore Oil Engineering Co., Ltd, Engineering Company)
Floating vessels moored in shallow water are at risk of possible bottom grounding and collision between the vessel and the subsea pipelines. Their dynamic responses are of great concern in offshore engineering. In this study, experiments were conducted to investigate the motion response of a large floatover barge moored in ultra-shallow water. White noise wave tests with five different incident angles were carried out in four different water depths. Shallow water effects were observed in the experiment. The motion characteristics of the moored barge in shallow water were also clarified in the analysis. The barge motions in the horizontal plane and the mooring line tensions increase with the decrease of the water depth, while the heave and pitch motions reduce. Results obtained from this study were provided to support the floatover installation operation.
According to the International Drilling HSE (Health, Safety, and Environment) management standards and advanced management experience as well as hazard management techniques, CNOOC (China National Offshore Oil Corporation) constantly improves HSE management objectives of offshore drilling platforms, HSE organizations and HSE operating specification in compliance with its particular drilling operation and development features, with the aim of in-place management and effective measures. During more than 30 years' drilling operations, CNOOC has already learned and summarized a set of drilling project HSE management systems, which have achieved good results. This article introduces the CNOOC Offshore Drilling HSE management organization and management system. Specifically, it presents the offshore drilling HSE guarantee measures from five aspects, which include field operation risk control, traffic safety, staff health, environmental protection, and emergency measures. Through the implementation of these management methods and measures, the CNOOC offshore drilling projects have gradually achieved the HSE management objectives: minor damage, low accident rate, and zero pollution.
Compact lithologic gas reservoirs, with poor connectivity between the formations, complex geologic feature and unpredictable production layers, have been mostly discovered with strong heterogeneity in Sulige Gas Field, which is characterized by ‘Four Lows', i.e. low pressure, low permeability, low production and low abundance. To solve these problems existing in this gas field, many tests and technical innovations have been made in the past 5 years to form the unique surface construction style of its own. This paper briefly introduces a series of new gathering technology and techniques adopted in the surface construction of Sulige Gas Field, i.e. downhole choking, no wellhead heating, no methanol feeding, concatenation of wells, measurement with liquids, medium/low-pressure gas gathering, normal-temperature separation, two-stage pressure boosting and centralized processing. Field experiences prove that the techniques mentioned above are fit for the development and construction of this gas field, thus providing helpful reference for the gas fields similar to Sulige Gas Field with ‘Four Lows'.
Key words: Sulige Gas Field; natural gas; gathering and transmission; process; technology; optimization; innovation
1. Geologic Feature of Sulige Gas Field and Difficulties in Development and Construction
There are great difficulties in development and construction of Sulige Gas Field which is a typical low porosity, low permeability and compact natural gas reservoir with complex geologic feature and strong heterogeneity. In addition, there exists the problems of low production output, rapid pressure decline and unstable production performance, characterized by ‘For Lows', i.e. low pressure, low permeability, low production and low abundance.
The CH4 content in local gas is above 90% (volume fraction, similarity hereinafter), whereas H2S content is lower than 20mg/ m3 and CO2 content less than 3%. Apart from a certain quantity (2%-8%) of C2~C6, the gas also contains a small amount of C7+ heavy hydrocarbon, averagely 1×104m3 of gas producing about 0.02m3 of condensate per day, so it belongs to wet gas with low carbon-sulfur ratio and low condensate.
On this account, it is an essential and urgent task to work out a set of self-owned surface gathering and transmission technology depending on the unique geologic feature of Sulige Gas Field by properly overcoming the following difficulties, mainly including:
(1) Low production of single wells, rapid pressure decline, unstable production performance, short life span of gas well, more wells required by unit production capacity, and harder investment control for surface construction.
(2) The producing pressure was as high as 22MPa in the earlier stage, but it declined rapidly. In most of the time gas production is under low pressure and it is difficult to determine system pressure.
(3) Gas wells have poor capacity of carrying liquid and wellhead temperature is low, resulting in frequent hydrate formation. If traditional methods against hydrate formation are used, methanol consumption will be great and the cost will increase.
(4) Both deoiling and dehydration are required because the gas stream contains a small amount of heavy hydrocarbon.
In view of the gels applied as plugging agents in drilling plugging and water plugging in oil and gas reservoir containing hydrogen sulfide (H2S), the effects of H2S on widely used gel blocking agents were studied in this article. The gel blocking agents include Na2Cr2O7/Na2SO3/HPAM gel, Na2Cr2O7/(NH2)2CS/HPAM gel, Cr(III)-acetate & Cr(III)-lactate/HPAM gel and phenol formaldehyde resin/HPAM gel. The results show that the effects of H2S on Na2Cr2O7/Na2SO3/HPAM gel and Na2Cr2O7/(NH2)2CS/HPAM gel are significant, while the effects on Cr(III)-acetate & Cr(III)-lactate/HPAM gel and phenol formaldehyde resin/HPAM gel are relatively slight. The mechanisms of H2S affecting the gels were also researched. For Na2Cr2O7/Na2SO3/HPAM gel and Na2Cr2O7/(NH2)2CS/HPAM gel, the H2S as reductant(the reducibility is more than that of Na2SO3 and (NH2)2CS) can reduce Cr(?) into Cr(III) and accelerate crosslinking reaction with HPAM in low concentration of H2S, while it can react with Cr(III) generating Cr2S3 precipitation in high concentration of H2S, for which the bulk gel can not form without Cr(III). For Cr(III)-acetate & Cr(III)-lactate/HPAM gel and phenol formaldehyde resin/HPAM gel, the changes are mainly affected by pH value. Therefore, according to the comprehensive survey of the effects of H2S on gel typed plugging agents, the phenol formaldehyde resin/HPAM gel is recommended as the plugging agents suitable for oil and gas reservoir containing H2S.
Xiang, Wentao (China National Offshore Oil Corp.) | Zhou, Wei (China National Offshore Oil Corp.) | Zhang, Jian (China National Offshore Oil Corp.) | Yang, Guang (China National Offshore Oil Corp.) | Jiang, Wei (Southwest Petroleum Inst.) | Sun, Lei (Southwest Petroleum Inst.) | Li, Jian
In South China Sea, the geological reserve of CO2 is huge. With the unanimous agreement of a series of problems caused by CO2 emissions, as an effective method to consume CO2, CO2 injection for enhanced oil recovery (EOR) has been investigated and reported by many researchers.
An extensive review of previous reported CO2-EOR projects is provided in this paper. According to exploring and analyzing the factors influencing CO2-EOR, and combined with the specialty of offshore conditions, reservoir evaluation of China offshore CO2-EOR is suggested in this paper. Based on the evaluation suggestion, the Chinese offshore oilfields were screened and the South China offshore oilfield close to CO2 reserve was conformable. This paper also describes the feasibility of CO2-EOR in the South China offshore oilfield from fundamental studies. The relationship of reservoir oil and CO2 showed that reservoir oil had good dissolving capacity to CO2. CO2 could effectively dissolve in and displace residual oil. The experimental results show that under reservoir conditions, CO2 could be in the one-contact miscible at 20 MPa, a slight higher than the formation pressure of 17.27 MPa. CO2 and oil could be in near miscible under formation conditions. The lab research work funded a further investigation on application of CO2-EOR in China offshore oilfield.
Zhong, Liguo (Daqing Petroleum Institute) | Cong, Haiyang (Drilling Technique Research Institute, Shengli Petroleum Administration) | Wang, Shiqing (The First Drilling Company, Huabei Oilfield) | Zhao, Defu (Downhole Operation Company, Daqing Oilfield Co. Ltd. CNPC) | Wang, Zhifeng (Drilling Tech. Research Inst. of Shengli Petroleum Administrative Bureau) | Yang, Guang (Downhole Operation Company, Daqing Oilfield Co. Ltd.)
The most challenging drilling problems encountered in Tahe Oilfield occurred in the deep salt formations. Most holes lost are caused by stuck drilling strings, stuck casing, and collapsed casing because of the special salt formations. Particular research is conducted to solve these problems. At first, the occurrence arose in salt formations are identified in detail. Then the components of typical salt rocks are analyzed, and properties such as plasticity, solubility, stability, and stress sensibility measured, some new techniques evaluated, and integrated techniques developed. As a result of implementation of the integrated drilling techniques, deep salt formations drilling in Tahe Oilfield has been substantially improved.
The main researching results presented in this paper are attached to the discussion of the salt formation problems, laboratory measuring and testing of the salt rock and evaluated techniques, and field drilling application. Integrated techniques recommended are particularized, such as borehole structure, salt water based mud system, expanding drilling and drilling string assemblies optimized.