In order to obtain highly talented microorganisms to be applied to Fuyu oilfield, PetroChina Company Limited Jilin Oilfield Company, where fractures and sedimentary anisotropy dominate the permeability of the reservoir, microorganisms which produce water-soluble polymer were searched for Microbial FOR by means of permeability modification. Enterobacter sp. TU-7A and TRC-322 were found among talented microorganisms which had already been obtained as gas producers, and Clostridium sp. TU-15A was newly obtained. All of these three microorganisms showed the viscosity of their cultivated solution equivalent to or higher than that shown by SP018 reported by Oklahoma University. Particularly, TU-15A showed an outstanding increase of viscosity, ca. 70cP at a shear rate of 40s-1. For simulative application of strain TU-15A to Jilin oilfield, its optimal cultivation condition and dominant growth under competitive reservoir conditions were discussed. Results may be summarized as follows. 1) The viscosity of cultivated solution for TU-15A proportionally increases with the initial molasses concentration, which makes possible an estimation of economically efficient concentration of molasses for injection, and moreover, which may make possible the use of fluid of so high viscosity that its injection is impossible through a well. 2) The optimum pH range of TU-15A for polymer production is 7.0-9.0. Automatic adjustment of pH to the optimum range may be done in the reservoir of Fuyu oilfield by natural dilution with brine, the pH of which is 7.7. 3) Initial cell concentration of TU-15A in the culture solution for injection must be equal to or higher than 1.0×106 cells/ml for its dominant growth in the reservoir.
The effect of five factors, CO2 partial pressure, H2S partial pressure, temperature, chloride content and bicarbonate content, on corrosion rate of API-13Cr and super 13Cr steels under sweet and light sour environments was systematically investigated and comprehensively analized. Since an essential reaction determining corrosion rate in CO2 environment is the direct reduction of carbonic acid, the carbonic acid activity becomes a key parameter to synthesize the effects of environmental factors, instead of pH. The CO2 corrosion rate is equated principally as a function of carbonic acid activity and temperature. The effect of slight amount of H2S and effect of alloying element content are also described quantitatively.
Bunduq Company Ltd. has been operating the field located 200km north-west from Abu Dhabi, UAE which straddles the offshore boundary between Abu Dhabi and Qatar in the Arabian Gulf since 1972. The extent of the field is 5 kilometers east to west, 6 kilometers north to south and has a reservoir 100 meters thick. Characteristics of its produce are API 40° and sulphur content less than 1%. The first stage development commenced in April 1971, but was later suspended in July 1979 due to a decline in the reservoir's pressure. As a result of simulated oil strata engineering studies, Bunduq decided to use a secondary recovery plan in which it boosted reservoir pressure and maintained it with water injection. The construction of all facilities related to the plan started in January 1981 and required a total of three years to complete. The Oil Field was originally held by concessionaire Abu Dhabi Marine Areas Limited (ADMA). When readying for secondary recovery, however, in April 1982 UPD (United Petroleum Development) obtained permission from the Abu Dhabi and Qatari governments to assume operatorship for all offshore activities. These operations included drilling, construction, production, and management. The operating condition of the field is severely corrosive where it contains high concentration of H2S (10.96mole%) and CO2(6.13mole%) gases. The H2S partial pressure and bottom hole temperature are 659 psi and 240°F, and the average water cut is exceeding 50%. This paper describes recent rigless remedial operations under such environment as following; (1) Gate milling operation with gate valve drilling machine (2) Water shut-off operation by Through Tubing Bridge Plug
Future targets of petroleum exploration will shift to stratigraphic traps, specifically turbidite reservoirs which are often distributed in deep-water environments. Therefore the demand for reducing exploratory risks will increase in exploring such subtle traps. Quantitative and stochastic models will be necessary for reservoir characterization and distribution prediction of such traps. Statistical analysis of bed thicknesses of turbidites is one of the most important methods for this purpose. In order to quantify bed thicknesses, it is essential to know how the bed thicknesses are distributed. Bed thickness distributions of turbidites have been interpreted as log-normal, power-law, exponential or truncated normal distributions. The identification of distribution laws, however, has been often difficult to interpret due to scattering of data and lack of quantitative tests in previous studies. In addition, the origins of distribution laws have been controversial and there has been no satisfactory interpretation. Although quantitative assessments of erosion in turbidite successions may give a useful parameter for reservoir characterization, their methods have yet been clarified. The identification and quantification of segments observed in the bed thickness distributions may give important insights for understanding depositional systems and reservoir characterization. If both of the volume distribution and the bed thickness distribution of turbidites are assumed to obey power law, the volume distribution can be estimated from the bed thickness distribution. This result would have a significant implication for stochastic modeling of reservoirs. Nevertheless the incompleteness of statistical methods, the bed thickness statistics can give useful information for 3-D reservoir modeling and predicting reserves.
SWD (Seismic While Drilling) using a drill bit as the seismic energy source while drilling is one of the techniques that can be used for obtaining time-to-depth information and formation image. The fundamental concept of SWD data acquisition and processing is briefly described in this paper.