Africa (Sub-Sahara) Algeria awarded four of 31 oil and gas field blocks on offer to foreign consortiums in its first auction since 2011. Shell and Repsol won permits for the Boughezoul area in the north of the country, while Shell and Statoil won permits for the Timissit area in the east. A consortium of Enel and Dragon Oil was awarded permits for both the Tinrhert and the Msari Akabli areas. Circle Oil's CGD-12 well, located onshore Morocco in the Sebou permit, encountered natural gas at different levels within the Guebbas and Hoot sands. Wireline logging analysis confirmed a net 9.7 m of pay. The first test, over the Intra Hoot sands, flowed gas at a sustained rate of 2.21 MMscf/D through an 18/64‑in. The primary target, the Main Hoot sands, flowed at a sustained rate of 4.62 MMscf/D through a 24/64-in.
Africa (Sub-Sahara) Shell's new natural gas discoveries in Egypt are estimated in initial quantities at about 500 Bcf with more reserves possible, said Aidan Murphy, chairman and managing director of Shell Egypt. The discoveries, in a concession area of north Alam El-Shawish in the country's western desert, could yield 10% to 15% of the total production of Badr el-Din Petroleum Company, the 50/50 joint venture of Shell and Egyptian General Petroleum Corporation that is expected to manage the operations. Eni reported that the Laarich East-1 oil well in Tunisia has a delivery capacity of approximately 2,000 B/D. Spudded in June, the well discovered hydrocarbons in Silurian and Ordovician sandstones while reaching a final depth of 13,487 ft. The well has now been connected to production. The company continues to drill Tunisian exploration prospects that have been identified on 3D seismic surveys.
Africa (Sub-Sahara) San Leon Energy reported encouraging performance from its OML 18 field in Nigeria. Reperforation of an oil well increased gross field production to approximately 61,000 B/D before output was temporarily scaled back to 53,000 B/D for a shut-in, upgrade, and workover of the well. A number of other field wells will be reperforated in coming months, the company said. San Leon holds a 9.72% interest in the field, which is operated by Eroton (35%). Nigerian National Petroleum Corp. holds the remaining stake. FAR said that drilling has begun on the SNE-5 appraisal well offshore Senegal. The well and the following SNE-6 well will evaluate the upper SNE reservoir units' connectivity and deliverability by oil flow testing that will include interference tests.
Cai, Junjie (Shenzhen Branch, CNOOC China limited) | Wen, Huahua (Shenzhen Branch, CNOOC China limited) | Gao, Xiang (Shenzhen Branch, CNOOC China limited) | Cai, Guofu (Shenzhen Branch, CNOOC China limited) | Hu, Kun (Shenzhen Branch, CNOOC China limited)
Huizhou Depression is in the exploration peak stage at present. The main target layer is gradually extending from the middle-shallow traps to the deep paleogene traps and the shallow lithologic traps, and the difficulty of exploration is totally increased. Paleogene layer oil&gas exploration is faced with the problems of deep buried depth, reservoir heterogeneity and uncertain distribution of high-quality hydrocarbon sources.
By combining tectonic evolution analysis with sequence stratigraphy, considering regional stress background and the utilizing of the seismic facies, the main faults tectonic features, stratigraphic sedimentary characteristics, the distribution position of sedimentary center and the control effect of the palaeogeomorphology on the sedimentary distribution range deposited from the transition zone are analyzed.
It is concluded that the lower Wenchang period's tectonic movement was dominated by the southern depression control fault, and the semideep-deep lacustrine high-quality hydrocarbon source rocks were mainly distributed in the south of the Huizhou Depression, such as HZ 26 Sag and the subsag of the XJ30 Sag. The braided river delta deposited from XJ30 transfer zone is mainly distributed along the west side of the long axis of XJ30 sag, and the semideep-deep lacustrine facies mudstone is formed in the east of XJ30 Sag. In the upper Wenchang period, the activity of the depression control faults in the northwest of the Huizhou Depression becomes stronger than the south, which influences the sedimentary center migrated from southeast to the northwest. The sediment provenance of XJ30 transfer zone deposits perpendicular to the long axis of the XJ30, and the long braided river delta is formed in the south side of the XJ24 Sag. In Enping period, which is changed from strong rift phase to rift-depression transition phase, the shallow lacustrine-swamp facies are taken as the main source rocks, and shallow braided river delta is widely developed, while the sediment from the provenance of XJ30 transfer zone is weakened.
The northern and southern migration of the transfer zone provenance river delta and the northern and southern distribution characteristics of the source rocks of semideep-deep lacustrine facies are caused by the differences of the northern and southern fault activities during the Paleogene period. Through the combination of structural evolution analysis and sedimentary characteristics analysis, the analysis of paleogeomorphology's effect on the control of sedimentary system is of great importance to the identification of high-quality paleogene reservoirs and hydrocarbon sources.
Oil and gas exploration in the deep-water areas have become a global hot spot. The deep-water area of the Baiyun sag in the Pearl River Mouth Basin is an important exploration target. The area is a typical deep-water hot basin of a wide range of geothermal gradients. Data from a single borehole shows a geothermal gradient from 4.0 to 6.64°C/100m. High geothermal field has an important control on the reservoir diagenesis, pore evolution and porosity-permeability trends. We analyzed sandstone samples from the ZhuJiang and ZhuHai Group, which were buried in the depth range between 500- and 4000m, and display similar composition and textures. The samples can provide insights into the evolution of reservoir diagenetic features under progressive burial process. We also analyzed sandstone samples frome EnPing Group. In general, the petrological composition was the main controlling factor of reservoir quality. The high geothermal field led to a rapid decrease in the porosity and permeability of deeply buried sandstones. Howerver, the EnPing Group, which has a deeper burial depth, shows good reservoir quality. Compared with the ZhuJiang Group and the ZhuHai Group sandstone, the EnPing Group sandstone is dominantly coarse sandstone with more quartz grains, minor feldspars and rock fragments. The EnPing Group is dominated by primary pores, which has a better porosity-permeability relationship than other groups. The deep-water of the Baiyun sag still has potential for exploration. In particular, EnPing Group sandstone reservoir may become a desirable goal in deep and ultra-deep exploration.
The paper mainly introduced the scenario research method and general design concept of FPSO in South China. According to the requirements of oil field production, the prospective future oil fields development surrounding the current oil field, operation safety and reliability, 150,000 DWT hull without propulsion capability is the final engineering scenario of FPSO hull. The permanent internal turret mooring system with disconnected function is recommended as the final scenario. The design criterion for the 500-year return is established according to the environment characteristic and operating experience. This paper presents the detailed FPSO design flow and method, the design principle, standard and new technology of FPSO in South China Sea, which can be a reference to other future FPSO designs in South China Sea and other similar projects.
Qi, Xiaoliang (COTEC Offshore Engineering Solutions) | Xie, Yi (COTEC Offshore Engineering Solutions) | Luo, Yong (COTEC Offshore Engineering Solutions) | Zhu, Weiquan (COTEC Offshore Engineering Solutions) | Gao, Wei (COTEC Offshore Engineering Solutions) | Shen, Hui (COTEC Offshore Engineering Solutions)
En Ping 24-2 oil field is located in the Pearl River Mouth Basin in the South China Sea En Ping Sag, about 200 kilometers south of Hong Kong in water depth of about 86-96 m. The development of En Ping 24-2 oil field includes a newly built eight-legged drilling and production platform (DPP) with drilling rig, living quarters, sewage treatment facility, utility systems etc. and 2.2km apart, a newly build 150,000 DWT FPSO with power plant, oil and gas treatment facilities, utility system and living quarters etc. The FPSO is kept in station by a single point mooring system of internal turret type.The single point mooing system and riser system design for the FPSO become the key issues in the project because both systems have to face new challenges, such as shallow water depth, wild environments and high fluid pressure.
The paper presents the key design parameters of riser system, and addresses the evaluation of riser configurations to suit the Enping development. The evaluation focuses on the technical aspects in terms of system feasibility in the presence of harsh Enping environment. With respect to the suspended dynamic riser, several widely used configurations are evaluated and conduct the dynamic analysis in order to obtain riser responses such as effective tension, bend radius, contact clearance and seabed touch. Finally the key conclusions are reached.
3D Petroleum System Modeling Study has been developed by using the Eni E&P Division internal package (e-simba™) in order to evaluate the petroleum potential of the Pearl River Mouth Basin, in the South China Sea.
Pearl River Mouth Basin is a Mesozoic-Cenozoic passive margin rift basin oriented NE-SW and parallel to the continental shelf. Within the Basin two main source rocks are recognised in the syn-rift succession: the organic levels of the Enping Formation, Oligocene in age and mainly terrestrial, and those of the Wenchang/Enping Formation, Oligocene/Eocene in age and mainly lacustrine.
Based on geochemical analysis of well data, the Enping source rock is modelled by using terrestrial kerogen type, TOC 1%, HI 250 mgHC/gTOC, 100 m of thickness and kinetics from analogue of Mahakam Delta. The Wenchang/Enping source rock is modelled by using lacustrine kerogen type, TOC 4%, HI 600 mgHC/gTOC, 100 m of thickness and kinetics from analogue of Green River.
Thermal data coming from wells and confirmed by literature suggest an average geothermal gradient of 35°C/km. The heat flow values at Present time match with well data. The creation of heat flow map was done by using a geostatistical approach, kriging with external drift method - software ISATIS, and by considering the correlation between the calibrated heat flow value at single well and the geological trend. Over the study area the heat flow trend correlates both with seismic and magnetic basement.
The results of thermal model integrated with geochemical well data (CO2 and gas maturity) show that the heating better correlates with seismic basement and allow to define the positioning of the organic matter level. A terrestrial source rock can be located in the shallower part of the Eocene/Oligocene sequence while a lacustrine one can be localised in the depocentral area at the base of the same sequence.
Deep and ultra deep low-permeability reservoirs are widely distributed in the South China Sea, such as HuiZhou 19-1, 26-3, 9-2 oil field and PanYu 34 gas field. These ultra deep reservoirs generally performed as deep burial depth, low porosity, low permeability, which lead to difficulty in evaluating well deliverability. DST is a fast and valid well test method for deep sands. The DST showed that layer M-31 of well HuiZhou 19-1 had a relatively higher productivity. However, the layer M-32 with the same perforated thickness only produced about 1.6 m3 each day. While the layer M-32 and M-31 has a vertical distance of about 25m and similar porosity and permeability. In order to evaluate well deliverability of layer M-32 and M-31, effect of mineral components and pore structure on DST was analyzed. 13 groups of start-up pressure and 13 groups of stress-sensitive experiments were also carried out. This work indicated kaolin clay in the soil minerals of layer M-32 damaged the formation and had an important impact on well deliverability from DST. In addition, layer M-32 offered an relatively high start-up pressure gradient, which reached the magnetite of 10-1 to 10-2. When effective stress was more than 15 MPa, the porous media would begin to deform seriously. The integrated approach indicated optimized production of the layer M-31 and layer M-32 of well are 2413.1 m3/d and 86.39 m3/d respectively. Numerical simulation also showed that enlarging producing pressure drop, hydraulic fracturing and horizontal wells can further improve well deliverability of deep and ultra deep low-permeability reservoirs. The study also suggested effect of kaolin clay and start-up pressure gradient on DST should be considered correctly.
This reference is for an abstract only. A full paper was not submitted for this conference.
More than ten gas pools in the shallow water region of the Pearl River Mouth (PRM) Basin and the Qiongdongnan (QDN) Basin, the Offshore South China Sea have been discovered since 1983. Gases produced from QDN Basin are characterized by high contents of benzene and toluene and relatively heavy delta13C2 values (-25- -27 permil), and the associated condensates by high abundance of bicadinanes and oleanane, which indicate a good correlation with the coal-bearing sequence of the Oligocene Yacheng Formation in the Basin. In contrast, the gases from PRM Basin contain lower amounts of benzene and toluene, lighter delta13C2 values(-24- -34 permil ), and a widely variable concentration of bicadinane and oleanane was identified from the associated condensates, which can be largely correlated with the Lower Oligocene Enping Formation source rocks formed in swamp to shallow lake in the Basin. The available geochemical data have indicated that both the Yacheng Formation and the Enping Formation from the basins contain mainly type III-II2 kerogen with dominant gas potential. The regional geological background indicates that the deep water regions of the two basins share the same hydrocarbon source sags with the shallow-water areas, and developed massive sandstone reservoirs during Oligocene and Miocene. Fluid flowing modeling results show that the deep water regions were on the pathway of lateral migrating gases, implicating to be favorable habitats for gas accumulation. In addition, the reservoirs in the zones have developed abundant bright spots which may reflect the presence of gas. Therefore, it is believed that there are great gas exploration potentials in the deepwater regions of the Offshore South China Sea, and the combination of geochemical data with basin modeling results will help to better define favourable targeting areas and reduce risk associated with the future deepwater exploration in the basins.