A pre-exploration well was drilled in the Xihu Sag of East China Sea basin, and commercial oil and gas flow had been achieved. But the oil and gas bearing trap had a big depth with low closure height and small area. The resolution of seismic data acquired by towed streamer is low, so it's difficult to obtain seismic velocity precisely. There were great risk and uncertainty in description of the trap and distribution of gas-bearing sandstone, reservoir prediction of sweet spot, direct hydrocarbon indication, and reserves assessment.
In consideration of the drilling platform on the trap, seismic acquisition technique of walkaway VSP and walk around VSP were introduced, meanwhile some innovative methods in source, receivers and geometry were applied. Twenty three-component hydrophones were composed as signal receivers which had a sample interval of ten meters in the well, two straight shot lines and two loop shot lines were designed around the drilling platform. Besides, volume and depth of air gun array were optimized, and the sailing route of seismic source vessel was planned properly in order to improve the efficiency of collecting work.
The collecting work of walkaway VSP and walk around VSP was accomplished efficiently, and more than seventy kilometers VSP seismic data was achieved. Afterwards, the new data was processed finely in company with zero offset VSP data, so high resolution VSP profiles and accurate seismic velocity were obtained. Reprocess to original seismic data acquired by towed streamer was implemented on the basis of walkaway VSP and walk around VSP data. The quality of normal seismic data was improved through reprocess constrained by walkaway VSP data, and S/N and resolution were much higher than old data. So it would be credible to research the distribution of gas-bearing sandstone and direct hydrocarbon indication using the reprocessed seismic data.
It was the first time to use joint acquisition technique of walkaway VSP and walk around VSP in offshore China which was an important breakthrough. High resolution VSP seismic profiles and precise seismic velocity could be acquired, and the data was important basis for refined evaluation of pre-exploration targets. It's very necessary to popularize and utilize these new techniques further.
Is Surfactant Environmentally Safe for Offshore Use and Discharge? The current presentation date and time shown is a TENTATIVE schedule. The final/confirm presentation schedule will be notified/available in February 2019. Designing Cement Jobs for Success - Get It Right the First Time! Connected Reservoir Regions Map Created From Time-Lapse Pressure Data Shows Similarity to Other Reservoir Quality Maps in a Heterogeneous Carbonate Reservoir. X. Du, Y. Jin, X. Wu, U. of Houston; Y. Liu, X. Wu, O. Awan, J. Roth, K.C. See, N. Tognini, Shell Intl.
By International Petroleum Technology Conference (IPTC) Monday, 25 March 0900-1600 hours Instructors: Olivier Dubrule and Lukas Mosser, Imperial College London Deep Learning (DL) is already bringing game-changing applications to the petroleum industry, and this is certainly the beginning of an enduring trend. Many petroleum engineers and geoscientists are interested to know more about DL but are not sure where to start. This one-day course aims to provide this introduction. The first half of the course presents the formalism of Logistic Regression, Neural Networks and Convolutional Neural Networks and some of their applications. Much of the standard terminology used in DL applications is also presented. In the afternoon, the online environment associated with DL is discussed, from Python libraries to software repositories, including useful websites and big datasets. The last part of the course is spent discussing the most promising subsurface applications of DL.
Jia, Hu (State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University) | Yang, Xin-Yu (State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University) | Zhao, Jin-Zhou (State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University)
Hu Jia*, Xin-Yu Yang, and Jin-Zhou Zhao, State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University Summary Foams can be used as well-killing fluid for workover operation in low-pressure oil and/or gas wells. However, foams usually come from gas injection under high pressure or high-speed stirring, which is complicated, expensive, and hazardous. In addition, the foam's stability is still limited by the current method of adding viscous polymer or the single crosslinking between the polymer and single crosslinking agent. This systematic study consists of optimization of different foaming agents, gel bases, and the effect of the GPC compositions (carbonate and acid) and their quantity, a macroscopic comparison of the stability and rheological properties of the double crosslinking and the common single crosslinking systems, with further investigation of their stability differences through microscopic research, and a coreflooding experiment to evaluate working performance. Within 4 days, the density of this novel foamed gel varies from 0.711 to 0.910 g/cm This is because of the function of the GPCs and foaming agent, which means that finer foams can be obtained to achieve target low density. Meanwhile, on the basis of the double crosslinking, a more compact gel structure is formed; thus the stability can be effectively improved. Results also demonstrated that this foamed gel shows a favorable performance of low fluid loss and temporary plugging, and the gas-permeability-recovery rate is up to 93.90%, which proves the gel to be effective for formation-damage control. This study suggests that the novel in-situ-generated foamed gel has the potential to achieve favorable well-workover performance in low-pressure and low-temperature reservoirs. Introduction In the later stages of mature oil-and gasfield development, workover is a frequent job for oil and gas wells. For safety consideration, pumping killing fluid into the wellbore is often a prerequisite to providing well control, even in ultralow-pressure reservoirs.
Na, Li (Faculty of Geographical Science, Beijing Normal University, 100875, Beijing, China) | Jinliang, Zhang (Faculty of Geographical Science, Beijing Normal University, 100875, Beijing, China) | Jinshui, Liu (Shanghai Branch, CNOOC Ltd., 200030, Shanghai, China) | Wenlong, Shen (Shanghai Branch, CNOOC Ltd., 200030, Shanghai, China) | Hao, Chen (Shanghai Branch, CNOOC Ltd., 200030, Shanghai, China) | Guangchen, Xu (Faculty of Geographical Science, Beijing Normal University, 100875, Beijing, China)
Summary The prediction of source rocks is very important to the basin at the initial stage of exploration, among which the description of the source rocks' spatial distribution and the evaluation of the source rocks' thickness are the most significant. For most of the oil and gas fields on the land, the prediction and evaluation of source rocks rely on geochemistry analysis. But well data is inadequate on the offshore exploration area. Therefore, seismic data and geophysical methods can be applied to improve the prediction accuracy of source rocks. Data and Method In this research, the main data relate to core, logging, seismic from Lishui Sag, China (Figure 1).
The sand reservoirs of Xihu Sag are mainly buried under 3000 meters, and have been deposited in a shallow water, high energy environment. These result in the sand reservoirs change quickly in lateral direction and have low porosity and permeability characteristics. So predicting the lateral change correctly and finding the effective reservoir featured with better porosity and high hydrocarbon saturation are the keys to successful exploration. Based on rock-physics analysis, the elastic parameters and their combination that can detect sand and effective reservoirs are established. Then the key steps of pre-stack simultaneous inversion are analyzed based on field data. The elastic parameters calculated by pre-stack inversion are used to guide the drilling location design of an appraisal well in Structure B.
Presentation Date: Tuesday, October 16, 2018
Start Time: 1:50:00 PM
Location: Poster Station 6
Presentation Type: Poster
Reservoir heterogeneity is the key factor which impact production, the water flooding efficiency and ultimate hydrocarbon recovery during the reservoir development. Reliable productivity evaluation from early stage is needed to understand reservoir characteristics and minimize the uncertainty of production potential, so that the solution could be prepared for the technical challenges in the development phase. Evolution of wells drilled at high overbalance with water-based mud typically shows the following challenges: severe near-wellbore formation damage, complex pore structures due to complex the lithology system and big discrepancy among permeability from different measurement source. The productivity analysis becomes complicated and affected by the interpretation methods under different measurement environment.
A comprehensive case study is presented in this paper for the productivity evaluation in high heterogeneous reservoir at high overbalance drilling. An integrated approach is elaborated to overcome the challenges by integrating all available data from data acquisition. Different scaled permeability from open-hole logs, MDT pretests, mini-DST and DST is integrated systematically to understand the vertical and horizontal direction of reservoir heterogeneity. From the integrated data analysis, the interpreted reservoir properties are upscale and populated into numerical model and validated through history matching by dynamic tests. This integrated methodology or study provides the attractive and efficient way to evaluate the productivity in the early stage of reservoir lifecycle, and it minimizes the uncertainty of production potential by understanding the reservoir characteristics. At the end, the suggestions are concluded according to this comprehensive study.
Guo, Hu (China University of Petroleum-Beijing) | Dong, Jiayu (No. 3 Oil Production Plant of Daqing Oilfield Company, Petro China) | Wang, Zhengbo (Research Institute of Petroleum Exploration & Development, Petro China) | Liu, Huifeng (Tarim Oil Company, Petro China) | Ma, Ruicheng (China University of Petroleum-Beijing) | Kong, Debing (China University of Petroleum-Beijing) | Wang, Fuyong (China University of Petroleum-Beijing) | Xin, Xiankang (China University of Petroleum-Beijing) | Li, Yiqiang (China University of Petroleum-Beijing) | She, Haicheng (Xi'an University of Technology)
This paper provides field scale EOR survey in China which is in line with biennial worldwide EOR survey published by Oil& Gas Journal (OGJ). The EOR progress in China is not available due to language difference and other reasons in OGJ EOR survey. From 2018, EOR survey in China will be published biennially. The first part of this survey mainly focuses on basic information. Chemical flooding, unconventional heavy oil, green recovery and natural gas recovery progress in China will be surveyed and discussed in detail in the other four parts elsewhere. The EOR projects including field tests and field applications in China are summarized in the same pattern as OGJ to the largest extent for better readership outside China. Most data is collected from published journal papers and reports. Different from other countries, there are only four major oil companies in China: CNPC, SINOPEC, CNOOC and Yanchang Oil. The 28 branch companies of these four companies are both operator and owners. Oil and gas production from CNOOC is all offshore. CNPC is the largest oil company in China and its oil production in 2016 accounts for 54% oil production in China. EOR survey in China includes chemical flooding (polymer, SP and ASP flooding, gas flooding (CO2, nitrogen and air), thermal production, MEOR, and foam flooding. EOR production in China in 2016 accounts for 18% total oil production, while chemical EOR accounts for 10 %. Up to present, there has been more than 34 ASP flooding projects in China, most in Daqing. The total ASP oil production in 2016 is 407 million tons. More than 30 SP flooding projects have been carried out, with incremental oil recovery factor of 7%-18% OOIP. More than 170 polymer flooding projects have been carried out. Polymer flooding has been used widely in Daqing, Shengli, Xinjiang, Liaohe, He'nan and Bohai. The incremental oil recovery from polymer flooding and ASP flooding is 7%-15% and 18%-30% OOIP respectively. Gas flooding in China is not as successful as chemical EOR. Polymer flooding production in the largest offshore oilfield in CNOOC accounts for 25% total oil production in 2016. While EOR production in China accounts for 15%-18% in recent years, however, the world EOR oil production only accounts for about 3.3% total oil production. EOR is greatly affected by oil price, as indicated from 26 years EOR content change in America. It is the first time that detailed EOR survey in China in line with worldwide EOR survey in OGJ is given. The EOR survey in China provides valuable and helpful information for engineers and researchers in oil and gas industry.
Hai Liu, Peiwu Liu, and Yongjie Huang, Schlumberger; Xufeng Xiao, Xiaojing Liu, and Meirong Tang, PetroChina Summary Activity in the Ordos Basin, China, has mostly occurred in the low-permeability, clay-rich Chang 7 sandstone, and has used multifractured horizontal wells as the preferred completion technique. To improve further the production potential and to increase operational efficiency, a dual-well pad site was engineered to try a paddrilling approach and to evaluate different completion techniques, use integrated work flows, and accelerate the development cycle. The pilot project involved two pads with two horizontal wells each, with the intention to compare the local multistage stimulation practice of using a tubing-conveyed completion method to a wireline-conveyed plug-and-perforation technique. The current tubingconveyed completion practice affects the completion efficiency of the well from the standpoints of surface efficiency, engineering work flow, post-fracturing performance, and subsequent commercial performance. The wells completed with the plug-and-perforation technique were completed in a shorter period of time; simultaneous operations enabled flowback water from the first well to be recycled and reused on pumping operations on the second well, further improving the project performance, and first-year cumulative production was 20% higher compared with surrounding offsets. Three vertical wells were placed between the parallel horizontal wells to enable real-time fracturing monitoring and to improve subsurface understanding. To have a more-precise microseismic mapping result, the closest vertical well was selected as the monitoring well. The study demonstrates the importance of an integrated approach that accounts for well design, engineering work flow, technology used during the execution, and subsequent evaluation while improving overall productivity.
Cai, Hua (CNOOC Ltd.-Shanghai) | Huang, Daowu (CNOOC Ltd.-Shanghai) | Duan, Dongping (CNOOC Ltd.-Shanghai) | Cheng, Chao (CNOOC Ltd.-Shanghai) | Ruan, JianXin (CNOOC Ltd.-Shanghai) | Li, Yangfan (CNOOC Ltd.-Shanghai) | Zhang, Xianguo (China University of Petroleum-Beijing)
Generally, the favorable diagenetic facies belt of the reservoirs is the dessert for hydrocarbon exploration. Traditionally, the research of diagenetic facies is based on core analysis, as a result, it is difficult to make prediction under the condition of sparse wells and less cores. In order to solve this difficulty, the new method to predict the diagenetic facies should be researched.
In this research, the low permeability sandstone reservoirs of East China Offshore Gas Fields are selected as the research area, and three research steps have been done. First, by using the core analysis, ACR (Apparent Compaction Ratio) and ADR (Apparent Dissolution Ratio) are selected as the discriminant parameters for the diagenesis, and the quantitative standards are established. Second, the rock-electric relationships according to the diagenetic facies are established, the relationship of well logging parameters (GR, DT, CNCF, RT, DEN) vs. ACR, and the same well logging parameters vs. ADR can be matched by using BP neural network method. Accordingly, the ACR and ADR of the whole well can be obtained, and the diagenetic facies in accordance with the ACR and ADR can be predicted. Third, the relationship of well-log and seismic data can be established. After that, the relationship of seismic attributes (Ip - p wave impedance, Is - s wave impedance, Vp/Vs - p and s wave velocity ratio) vs. ACR, and the same seismic attributes vs. ADR can be matched. After the three steps, the favorable diagenetic facies belt can be predicted by using seismic attributes under the condition of sparse wells and less cores.
By using the above methods, the diagenetic facies in the research area can be divided into six types: mid dissolution and mid compaction; mid dissolution and mid-strong compaction; strong dissolution and strong compaction; mid-strong dissolution and strong compaction; shale-silty strong compaction; strong cementation. The previous three of the six types are selected as the favorable diagenetic facies. According to the quantitative standards of ACR & ADR, and the relationship of the seismic attributes vs. ACR & ADR, the diagenetic facies in the plane and vertical can be predicted by using seismic attributes. In the research area, three layers of Huagang formation have been selected by fitting the favorable diagenetic facies: Layer 1 (Shallow) corresponding to mid dissolution and mid compaction; Layer 2 (Mid) corresponding to mid dissolution and mid-strong compaction; Layer 3 (Deep) corresponding to strong dissolution and strong compaction. As a result, these three layers are considered to be the desserts for exploration and development.
This paper presents a new quantitative characterizing system for diagenetic facies by combing core-logging-seismic. Furthermore, a new method to quantitative characterizing diagenetic facies by using seismic attributes is established for the first time. The innovative content presented in this paper can provide theoretical references for exploration of sandstone reservoirs under the condition of sparse wells, and also provide complement for the diagenetic facies characterizing theories.