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Construction of an efficient development mode for buried-hill fractured reservoirs in Bohai Bay.

QHD32-6 is typical offshore heavy oil filed with about 1.1 BSTB of OOIP and with a very complex fluvial reservoir in Bohai Bay, China. The field was developed by CNOOC, Texaco and Arco in 1998. Based on the Original Field Overall Development Plan, the forecasted waterflooding recovery was about 17.4% OOIP due to the complex sand and OOWC, high crude viscosity and active bottom and edge water.After starting production, the water almost broke through immediately in many producers and the oil production was disastrously declined. After two years operation practice, oil recovery was downsized to 13.4% in 2003. An integrated reservoir management program to improve oil recovery was initiated in 2003. The reservoir characterization was re-visited in detail with new data from development practices, infill well drilling, and dynamic production analysis. The comprehensive program was developed which including (1) water management; (2) infill drilling; and (3) EOR.The key of water management is to control the rise rate of water cut. The program includes separated water, plugging sands with high water cut, maintaining reservoir energy by smart water injection, and injection profile improvement. The rise rate in water cut was significantly changed from 20% per year down to 3.5% per year.Infill drilling was initiated in 2004 and is gradually and successfully expanded to the entire field based on the study of remaining oil distribution. So far, 36 out of 37 infill wells were added to production and showed a good performance.For EOR practice, a field trial of cross-linked gel injection is implementing. The pilot test study of polymer flooding and N 2 Foam flooding are conducting now. QHD32-6 field has achieved a 0% of decline since 2006 and the production rate even jumped from 28,300 BOPD to 33,200 POBD in 2010 or increases 17.3%. The forecast waterflooding recovery has changed to 24% based on the field operational practices. It indicates a good reservoir management can be a critical operation strategy to the marginal field development.The successful application of reservoir management is leading the secondary development of this field. It is expected the EUR by the end 2030 by waterflooding and EOR processes will reach 35%. It provides a good example in Bohai Bay.

Abstract:With the increasing proportion of gas cap & artificial gas injection reservoirs, production performance monitoring and evaluation of gas-drive reservoir are becoming more and more important. However, there is no efficient method to forecast the production performance of gas-drive reservoir. In this paper, the analysis starts from the statistics of oil/gas relative permeability data of cores experiments. Based on fundamental principles of segregated flow and material balance, a new analytical curve of gasflood was developed to analyze the production performance. We applied the novel analytical curve to the production data from 23 gas-drive reservoirs at home and abroad and found a better power function relationship between dynamic reserves (N d ) and the slope (B) as foreseen by the analytical curve. It has been shown that the slope of the new curve represents dynamic reserves value; the smaller the slope value is, the more dynamic reserves are. Furthermore, by introducing the economic limit gas-oil ratio and control conditions which include initial and boundary conditions, a chart of dimensionless fractional flow of gas vs. recovery percent of OOIP is established to evaluate oilfield development rapidly and intuitively. Finally, many examples of application confirmed strongly that the new analytical curve used in gas-drive reservoirs is practical and effective, which broadens the scope of gas-drive oilfield research.

JZ25-1S oil field located in Bohai bay which has a thin oil rim with a gas cap on top and aquifer below, and this field has to supply fuel gases to the residents. To achieve maximum oil recovery, force balance between aquifer drive, gas cap expansion, and viscous withdrawal shall be carefully studied for this type of reservoir at various stages of the production lifecycle. Available methodologies including analytical, and simulation are used to optimize the development strategies, including well type, the well location, drawdown and so on. Using horizontal wells to develop the thin oil rim, the horizontal length parallels with the GOC and OWC, the horizontal section length is 300–400 m nearby, the stand off over the OWC is 1/3 of the oil column if the gas capindex is more than 1.5, and the optimized drawdown of the horizon well is recommended 0.3–0.6MPa ; while the gas capindex is less than 1.5 and the aquifer is stronger, the stand off over the OWC is 1/2 of the oil column, the drawdown is recommended 0.5–0.8MPa; And making good use of the gas and aquifer energy at initial stages of production, then using water flooding for the reservoir which gas cap index is less than 1.5 and the aquifer is weak. A number of horizontal wells were optimized and drilled in JZ25-1S field after optimizing the development strategies. The initial oil rates are from 943-2830bbl/d under the optimized drawdown. The management of GOC and OWC movement is extremely critical in this kind of oil field. Based on the achieved parameters, these wells display significant higher oil production with delayed water coning and slower gas channeling. Both simulations and production data demonstrate that the JZ25-1S development strategies gain success, using horizontal wells balance GOC and OWC to explore hydrocarbon, and achieve maximum results, which provides the theoretical and production data for development optimization of thin oil rim reservoirs with gas cap in Bohai Bay.

Background The purpose of this study was to survey the associations of six single nucleotide polymorphisms (SNPs) in the TMOD1 and PTCSC2 genes with thyroid carcinoma (TC). Method Peripheral blood samples were obtained from 510 patients with TC and 509 normal controls. Six SNPs were genotyped by the Agena MassARRAY platform. Logistic regression was used to evaluate the association between SNPs and TC susceptibility by calculating odds ratios (ORs) and 95% confidence intervals (CIs). SNP-SNP interactions were analyzed by multifactor dimensionality reduction (MDR). Results Our study showed that rs925489 (OR = 1.45, p = 0.011) and rs965513 (OR = 1.40, p = 0.021) were significantly associated with an increased risk of TC. Rs10982622 decreased TC risk (OR = 0.74, p = 0.025). Further stratification analysis showed that rs10982622 reduced the susceptibility to TC in patients aged ≤ 45 years (OR = 0.69, p = 0.019) and in females (OR = 0.61, p = 0.014). Rs925489 increased TC risk in people aged > 45 years (OR = 1.54, p = 0.044) and in males (OR = 2.34, p = 0.003). In addition, rs965513 was related to an increased risk of TC in males (OR = 2.14, p = 0.007). Additionally, haplotypes in the block (rs925489|rs965513) significantly increased TC risk (p < 0.05). The best predictive model for TC was the combination of rs1052270, rs10982622, rs1475545, rs16924016, and rs925489. Conclusion TMOD1 and PTCSC2 polymorphisms were separately correlated with a remarkable decrease and increase in TC risk based on the analysis.