In 2001, a multi-stage hydraulic fracturing treatment was successfully completed inMinami-Nagaoka gas field, Japan. The well productivity was increased eight times higher than theoriginal. The main factor for the success is the understanding of the mechanism of multiplefracture near the wellbore. The new theory explained how two treatments conducted in 1990 and1992 failed due to premature screen-outs. The third fracture treatment was significantly improvedby suppressing tortuosity with many changes in job design based on the new theory of fracturingmechanism. Changes include vertical well profile, high rate injection of high viscosity gel, improved perforation technique, breakdown injection and proppant slug. In addition, fracturingtreatment was repeated six times using sand plug technique. Before applying this improvedfracturing technique to others wells in Minami-Nagaoka or other fields broadly, furtherimprovements are required for the higher rate of success and efficiency. Those improvements are(a) optimization of fracturing design including proppant slug strategy (b) cost reduction byeliminating non-contributing improvements and shortening of job cycle (c) flexible treatmentdesign with continuous gel mixing (d) improved flowback system to avoid surface facilityerosion.
Yufutsu field is located in the southern Ishikari Plain, central Hokkaido, in northern Japan. Japex commenced the production in 1996 and is producing gas and condensate. The reservoir is a naturally fractured granite and conglomerate. The permeability and porosity is very low. The reservoir is so heterogeneous that it cannot be modeled with the conventional method. We modeled it with the discrete fracture network (DFN) model by using the statistical properties of the fractures extracted from static data such as borehole images. The borehole images show that the fractures can be divided into two families according to the nature. One includes fractures of wide apertures. This family keeps a clear tendency of the azimuth and dip. The other includes narrow aperture fractures whose azimuth and dip are more scattered. Two sets of DFN model were made and merged to one model to make an overall DFN model. The model was calibrated successfully with the dynamic data such as pressure buildup data and production history. The pressure buildup data were used for the calibration of fracture properties and the production history were used for the calibration of spatial distribution of fractures.
Upon the signature of The Production Sharing Contract (PSC) and Joint Operating Agreement (JOA) for Block SK-10, Offshore Sarawak in November 1987 among Petronas, Nippon Oil Exploration (Malaysia) Limited (NIPPON) and Petronas Carigali Sdn Bhd (PCSB), NIPPON conducted exploration activity in the block. Coming from the gas discoveries in Helang area, Petronas, NIPPON and PCSB signed the “Upstream Gas Development and Sale and Purchase Arrangement relating to SK-10 PSC” in August 1995 for the purpose of developing gas fields for supply to Bintulu Sarawak, primarily to the proposed LNG-3 plant. Through conducting various technical studies and deliberation, Field Development Plan (FDP) was finalized and approved by Petronas in 1999. Facilities construction works have been initiated thereafter and continues to date. Every effort has been and being made toward first gas production from Helang Gas Field in October 2003. In the course of field development work, series of investigations have been made on the focused items, which can be considered as technical features of Helang Gas Field development. Introduction of the milestones to date and future of Helang Gas Field Development activities and technical features adopted in production facilities and development wells are presented in this paper.
It has been over 30 years since MOECO was awarded exploration rights in the Gulf of Thailand. MOECO has been carrying out exploration for oil and gas in this area since 1971. During that period, the Erawan gas field was discovered in Thailand in 1973 and its production started in 1981. In turn, other gas fields were discovered. Currently, the average gas production is 740 mmcf per day produced by 13 offshore gas fields. In 1999 the Pailin gas field, Block B 12/27, in the gulf of Thailand began production. The current gas production of the Pailin field is approximately 330 mmcf per day. In order to achieve long term financial success in the gulf of Thailand, where geological structures are extremely complex and reservoir extents are marginal, an operator has been required to drill many wells at an absolute minimum cost. Throughout the last 20 years of these field's productive lives, important initiatives have been undertaken by UNOCAL, as an operator, to meet numerous technical and economic challenges. I will introduce an overview of some of technical challenges in the fields, such as 3 D seismic, drilling innovation including simplified and slimhole well design, PDC bit, mud system, unitized wellhead, installation of top drives, steerable system and adjustable guage stabilizer, completion design, MWD etc.
The continental shelf of the U. S. Gulf of Mexico (GOM) is considered one of the most matured and overexploited oil and gas basins in the world. In fact, most of the large E & P companies have shifted their operational area to the deepwater since mid 1990s when Mineral Management Services (MMS) announced an incentive scheme on the federal royalties. Despite such circumstances, it is true that the GOM continental shelf still remains an important revenue source to such companies and it turns out that the area is the second largest oil and gas producing area (after Alaska) in the North America. One of the unique features in GOM is that the “niche” business exists and is growing along with the change of large companies' focus in their activities. Some niche players with sound business models have been demonstrating substantial growth in recent years, which, together with current eye-catching “deep Miocene” exploration, are helping to take the GOM into a new era. Mitsubishi Corporation (MC) has been aware of such a unique business environment in the GOM through their in-house studies, as well as their thorough monitoring on the local industry. MC has now reached such a level of confidence that they can establish a sustainable business without exposing themselves to an excessive risk associated with exploratory drillings. They have thoroughly examined several niche businesses to build an optimum business model to them. As a result, they have come to a conclusion of building a business model based on monetizing marginal proven undeveloped oil and gas discoveries (PUD).
This paper introduces the feature of JNOC GTL process and part of the results of Yufutsu GTL pilot plant test. JNOC GTL process and catalysts have been developed by collaboration with five Japanese companies such as Japan Petroleum Exploration Co., Ltd, CHIYODA CORPORATION, COSMO OIL Co., Ltd, NIPPON STEEL CORPORATION, and INPEX CORPORATION. We succeeded in producing the first GTL from natural gas November in 2002 at Yufutsu GTL pilot plant. We have been verifying the performance of syngas catalysts and FT catalysts and seizing the engineering data for scale-up under the pilot plant's operation.
Natural gas and gas base liquid fuels such as FT (Fischer-Tropsch) Diesel are expected as clean fuels. Natural gas consumption is evaluated to be increasing rapidly within next 30 years. Now, a lot of changes are observed in natural gas and LNG trade and the competition in the gas trade is coming to severe. But, because a large investment is required for LNG project and pipeline project, sharing of risk and profit and cooperative competition between suppliers and buyers are important to stably supply enough natural gas to the market. Conversion of natural gas to liquid transportation fuels and other specialty products is seen as a potentially attractive means of monetizing “stranded” gas. A large number of potential commercial-scale GTL (gas-to-liquid) projects are now being planned with a capacity totaling 1.6-1.8 MMBPD. Based on the market studies, it was evaluated that there are potential markets for GTL products, especially FT Diesel and FT Naphtha, and that timing of the start-up and further cost reduction are keys to successfully introduce these products to the market.
Chemical compositions of methane (C1), ethane (C2), and propane (C3) of natural gases from their production wells in Japan were measured for clarifying mechanisms of their generations in combination with δ13Cc1 values. Natural gases having δ13Cc1 values of -70‰ to -62‰ give extremely high C1/(C2+C3) ratios of 1, 000 to 6, 900 and little C2 and C3 contents (lower than 0.1% and 0.05%, respectively), indicating that they are generated by microbial decomposition of organic matter in the formations. As δ13Cc1 values of natural gases increase from -60‰ to -50‰, their C1/(C2+C3) ratios decrease sharply from about 1, 000 up to 2, because of extreme increases of C2 and C3 contents up to about 10%. Furthermore, as their δ13Cc1 values increase from -40‰ to -30‰, their C1/(C2+C3) ratios increase again, showing that natural gases having δ13Cc1 values from -50‰to -40‰ give the lowest C1/(C2+C3) ratios. These results indicate the existence of metathermogenic gas proposed as an intermediate between microbial and thermogenic gases by Kita et al. (2001) and support their proposal that -40‰ of δ13Cc1 value can be defined as the boundary between meta-thermogenic gas (MTG) and thermogenic gas (TG) based on the relationship between δ13Cc1 values and N2/Ar ratios. Furthermore, the sharp decrease of C1/(C2+C3) ratios in the range of δ13Cc1 value from -60‰ to -50‰ indicates that -60‰ of δ13Cc1 value can be used as the boundary between microbial gas (MG) and meta-thermogenic gas (MTG). On the other hand, the relationship between C1/(C2+C3) ratios and δ13Cc1 values of natural gases is similar to that between their C1/C2 ratios and δ13Cc1 values. This indicates that C1/C2 ratio can be used instead of C1/(C2+C3) ratio for discussing their origins in combination with δ13Cc1 value.
Diatom and calcareous nannofossil biostratigraphy was established for the PlioceneKuwae Formation along the Natsui stratigraphic section, Tainai River, Kitakanbara area in NiigataPrefecture, central Japan. Three useful diatom biohorizons, the FO (first occurrence) ofNeodenticula koizumii; RI (rapid increase) of N. koizumii and LO (last occurrence) of Neodenticulakamtschatica along with calcareous nannofossil datum A defined by Sato and Kameo (1996) wereidentified in the formation, which established a precise chronologic framework of the Natsuisection. Fresh water diatom fossils and reworked Miocene diatom valves occurred throughoutthe section and the proportion of these taxa fluctuates in a frequency of several tens ofthousands years. Sporadic occurrences of warm water diatoms such as Hemidiscus cuneiformis, Nitzschia reinholdii and Rhizosolenia bergonii were recognized at several horizons. Among these, theoccurrence at the horizon just above the FO of N. koizumii was found both in the present sectionand in the Yabuta Formation in the Himi area, which suggests its probable correlation.
The magnetostratigraphy for the uppermost part of the Pliocene Kuwae Formation was established along the Tainai River (Natsui Section) in the Niigata Prefecture, Japan. Characteristic components were identified from fourteen sites out of 60 collected sites through the progressive thermal demagnetization (PThD) test, but no stable component was recognized for all pilot specimens through the progressive alternating field demagnetization (PAFD) test. After the tilt-correction for inclined sites, the normally and overlying reversely magnetized sequence was recognized. Combining with biostratigraphic-age constraints, the normal and following reversed polarity sequence can be correlated to the uppermost part of the Gauss (C2An.1n) and the lowest Matuyama (C2r.2r) Chrons. Thus the Matuyama/Gauss boundary (2.581Ma) is located at the uppermost part of the Natsui Section, which gives an upper limit for the underlying marine sequence of the Pliocene Kuwae Formation.