Micropore Structure Characteristics and Recoverability Evaluation of Typical Shale Oil Reservoirs

In view of the weak research on the availability of typical shale oil reservoirs from the perspective of development, this study introduced a two-dimensional nuclear magnetic resonance (NMR) evaluation method on the basis of the previous one-dimensional NMR combined with centrifugal physical simulation experiments. Not only the production characteristics of typical shale oil reservoirs were studied but also the microscopic production laws of different occurrence states were studied. The results show that the pore distribution of Jilin shale is more concentrated than that of Qinghai shale. The oil of the two blocks mainly occurs in 0.01–10 ms pores, and the occurrence ratio of Jilin shale in the pores is higher, which is more than 90%. The oil production of the two blocks is mainly dominated by 0.01–10 ms pores, and the utilization efficiency contribution of these pores in Jilin shale is higher, accounting for about 80%. The utilization efficiency (UE) increases logarithmically with centrifugal force, and the growth rate of Jilin shale is greater than that of Qinghai shale. The proportion of free oil in Jilin block is less than that in Qinghai block. The shale oil in the two blocks is both at 15% final UE, and the UE of free oil in Jilin shale is about 9% and that of Qinghai shale is about 12%. The recoverability of Jilin shale is lower than that of Qinghai shale

Calculation model of on-way parameters and heating radius in a superheated steam injection wellbore

As superheated steam is a single-phase gas, it does not fit theories of ordinary steam heat loss calculation models based on two-phase flow. By using the PVT data of superheated steam, this paper builds a calculation model of on-way parameters in the superheated steam injection wellbore. The superheated steam heating area and heating radius formulae are presented. The calculated results for on-the-way change of steams in Well X16 of the Kenneyak oilfield fit well with the field test results. The analysis shows that the temperature of superheated steam varies greatly with heat transfer, the pressure varies greater than for ordinary steam, the steam quality is high when reaching the bottom hole, the steam enthalpy is much higher than for ordinary steam, and the heating radius is wider. 摘要: 过热蒸汽是单相的气体, 以气液两相流理论为基础的普通蒸汽热损失计算模型对其不再适用。通过引入过热蒸汽PVT数据体, 建立了注过热蒸汽井筒沿程参数计算模型。在一定假设的基础上, 理论推导出了过热蒸汽带面积、加热带半径等的数学表达式。利用蒸汽沿程参数计算模型对肯基亚克油田盐上油藏X16井不同状态水蒸汽的沿程变化进行了计算, 结果表明: 计算结果与现场测试结果对应较好。分析认为, 随着热量的传递, 过热蒸汽的温度变化较大, 压力变化也大于普通蒸汽, 到达井底的蒸汽干度特别高, 其热焓值比注普通蒸汽有大幅度提高, 加热半径也有所增加。 Key words: heavy oil, superheated steam, on-way parameter, heating radius, calculation mode

Discussion on effective development techniques for continental tight oil in China

Based on the main geological features and technical breakthroughs made in tight oil exploration, the major challenges facing tight oil development are analyzed, and the key technical trend for tight oil development is discussed in this paper. Mainly found in continental deposits, tight oil reservoirs in China feature small area, poor physical properties, big differences in geological characteristics between different basins, but low porosity, low permeability and pressure in general. In contrast to marine tight oil, tight oil in continental deposits faces such challenges as low production and recovery, and poor economics. Through nearly three years of research and pilot test, an integrated development mode with repeated fracturing of horizontal wells as the principal technique has been proposed, which includes integrated design, platform long horizontal well drilling, massive volume fracturing, re-fracturing stimulation, controlled production, factory-like operation, concentrated surface construction etc. It is recommended that study be strengthened on basic tight oil development theory, practical development technologies, and economic evaluation of tight oil development over the whole life cycle. Key words: continental tight oil, geological characteristics, effective development, key techniques, repeated fracturing of horizontal well

Analysis on the mechanism of the enforced imbibition effect of tight oil reservoir by the activated water

Based on the parallel rock samples of tight oil reservoirs, the imbibition comparison experiments respecting to formation water and active water under different experimental conditions have been initiated. With adoption of the experimental measures i.e. Nuclear Magnetic Resonance (NMR), the micro-production mechanism of the enforcement of the imbibition oil recovery effect by the active agent has been analyzed. Surfactant may promote the imbibition effect of samples with different wettability, different water saturation and different sizes. The imbibition recovery ratios of No. 1 hydrophilic core in formation water and active water are respective 15.79% and 17.68%, and the active water imbibition increased by 1.88%, with an enforcement ratio of 11.97%. The imbibition recovery ratios of No. 3 lipophilic core in formation water and active water are respective 10.64% and 13.26%, and the active water imbibition increased by 2.62%, with an enforcement ratio of​ 24.62%. The enforcement effect of surfactant on the lipophilic core is higher than that on the hydrophilic core. The enforcement ratio of No. 1 core in macropores is 8.78%, and that of No. 3 rock is 36.14%, indicating that the surfactant can effectively reduce the seepage resistance of the lipophilic cores and enhance the imbibition recovery ratio of macropores. The increase magnitude and the enforcement ratio of the imbibition recovery of No. 4 low water-contained core are lower than those of No. 6 high water-contained core, indicating that the surfactant has a greater impact on the imbibition of high water-contained cores. The enforcement ratio in active water imbibition in core No. 4 is 28.59% in micropores and 15.46% in macropores; and respective 1460.74% and 9.56% for No. 6 core. The enforcement ratios of micropores in the two cores are both higher than those in macropores. It shows that the surfactant has a great influence on the permeability of micropores in the core. The increment magnitude in active water imbibition of small No. 2 core is 22%, and that of No. 2 large core is 26.93%, indicating that the surfactant has a greater impact on the imbibition of large cores