Mesoscale eddies play an important role in transporting North Pacific subtropical mode water (STMW). Using eddy samples adopted from a 3‐day and 0.1° ocean model output spanning from 1980 to 2014, this study quantifies the eddy‐trapped STMW volume and transport south of the Kuroshio Extension. Based on the shape of their isopycnals, anticyclonic eddies (AEs) in the region are classified into two types. The first type (AE1) has a lens‐like structure of isopycnals, and the second type (AE2) has downward bending isopycnals throughout the pycnocline. In contrast to AE2, a cyclonic eddy is characterized by upward bending isopycnals throughout the pycnocline. Although all three eddy types can trap STMW, the low potential vorticity water within an AE1 is found to be thicker in the spring and better preserved through the rest of the year. A quantitative estimation finds that the STMW volume trapped by an AE1 is approximately 1.5 and 2.5 times larger than the volumes trapped by an AE2 and a cyclonic eddy, respectively. The eddy‐trapped STMW moves primarily westward, with its meridional integration between 25 and 35°N reaching ~1 Sv at 143°E, approximately 17% of the time‐mean total zonal STMW transport there. This study highlights the important role of eddies (particularly the AE1) in carrying STMW westward and thus modulating North Pacific climate variability.
The exploration and development of offshore oilfield facing unprecedented challenges include the decline in the quality of oil reserves, increase of invest and strict environmental protection policies. Usually, low permeability reservoir, heavy oil reservoir complex fault block and small reservoir located far from an existing facility are classified into marginal oilfield. More and more marginal oilfield is put on the schedule of development. In the view of economic, The internal rate of marginal oilfield return is lower than the benchmark rate of return of the industry, but higher than the cost discount rate of the industry. An integrated work flow is presented to improve the tap the potential and mitigate the risk of marginal oilfield involved in dependent development of small oilfields, unit exploitation of small oilfield group, simple platform, extended reach well and phased development. The LD oil field is taken as an example to state the strategy of marginal oilfield.
The prediction of reservoir fluid production law play a key role in offshore oil field development plan design. It determines the parameter selection of pump displacement, oilfield submarine pipe capacity, platform fluid handling capacity, power generation equipment, etc. If the liquid production forecast is too low, the capacity will be expanded later, while if the forecast is too high, it will result in a waste of investment, which directly affects the fixed investment in oilfield development. Based on the statistical analysis of big data, this paper applies the dynamic data of all single wells and full life cycle of the oil field to analyze the dimensionless liquid production index (DLPI) law, and further establish the liquid production index prediction formula on this basis. Thus, the different types of Bohai plate and statistical table of the characteristics of the DLPI of the reservoir are completed. The results show that the DLPI of Bohai Sea heavy oil reservoir are following: water cut < 60 % indicates the trend is flat; water cut between 60 ∼ 80 % illustrates the slow growth (water cut 80 % is 2.5∼3 times); water cut > 80 % shows rapid growth (water cut 95% is 5.5∼6 times). The DLPI of Bohai Sea conventional oil reservoir are as following: when the water cut < 60%, the DLPI drops first, and then increase when the water cut is about 30% (the lowest point (0.7∼0.9 times)). When the water cut rise to 60%, the DLPI returns to 1 times; When the water cut is 60∼80%, it grows slowly (1.5∼2 times); when the water cut > 80 %, it grows rapidly (water cut 95% is 2∼3 times). The study may provide a guidance to the prediction of the amount of fluid in offshore oilfields, provide a basis for the design of new oilfield development schemes and increasing the production of old oilfields.
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