Application of a proportional-integral control for the estimation of static formation temperatures in oil wells

A strategy based on proportional-integral (PI) feedback control was applied to solve an inverse heat transfer problem for estimating static formation temperatures (SFTs) from logged temperatures in oil wells. The PI control feedbacks the error between logged and simulated temperatures during the shut-in time process, existing SFT proposal. Thus, mathematically speaking an inverse heat transfer problem was solved in this way, since SFT represents the initial conditions (which are unknown) to solve the partial differential equations governing the heat transfer process in the wellbore-formation system. The mathematical model considers transient convective heat transfer due to circulation losses to the rock surrounding a well. The methodology was tested analyzing two oil wells (MB-3007 and MB-3009) from the Gulf of Mexico and results were compared against two classic methods. The method presented in this work needs only one temperature measurement for each fixed depth to estimate the SFT.     

镇泾油田红河105—1057井区微生物异常与含油气性关系

油气微生物勘探（MPOG）是地表油气藏评价的一个分支,主要研究近地表土壤层中微生物异常与地下深部油气藏的相关关系,它以成本低廉,简便快速,多解性小的特点,在镇泾油田得到充分的验证。在镇泾油田内,以微生物异常为基础,结合已有的区域油气地质、钻井和测井等资料,对微生物异常区域进行分析研究,重点解释说明了镇泾油田红河105—1057井区长821小层与油气异常的关系,并圈定出2个异常区,其异常连片分布,异常区的异常平均值较高,反映本工区内油藏控制面积较大。本工区天然气微生物异常整体水平较低,且基本上与油藏微生物异常区吻合,异常区零星分布,表明本工区的天然气多系原油溶解气。最后对工区油藏分级评价,并根据微生物勘探结果和地质特征等综合因素,在工区部署3口建议井。     

Effects of oil expulsion and pressure on nanopore development in highly mature shale: Evidence from a pyrolysis study of the Eocene Maoming oil shale,south China

The influence of oil-expulsion efficiency on nanopore development in highly mature shale was investigated by using anhydrous pyrolysis (425–600 °C) on solvent-extracted and non-extracted shales at a pressure of 50 MPa. Additional pyrolysis studies were conducted using non-extracted shales at pressures of 25 and 80 MPa to further characterize the impact of pressure on pore evolution at high maturity. The pore structures of the original shale and relevant artificially matured samples after pyrolysis were characterized by using low-pressure nitrogen and carbon-dioxide adsorption techniques, and gas yields during pyrolysis were measured. The results show that oil-expulsion efficiency can strongly influence gas generation and nanopore development in highly mature shales, as bitumen remained in shales with low oil expulsion efficiency significantly promotes gaseous hydrocarbon generation and nanopore (diameter < 10 nm) development. The evolution of micropores and fine mesopores at high maturity can be divided into two main stages: Stage I, corresponding to wet gas generation (EasyRo 1.2%–2.4%), and Stage II, corresponding to dry gas generation (EasyRo 2.4%–4.5%). For shales with low oil expulsion efficiency, nanopore (diameter < 10 nm) evolution increases rapidly in Stage I, whereas slowly in Stage II, and such difference between two stages may be attributed to the changes of the organic matter (OM)’s mechanical properties. Comparatively, for shales with high oil expulsion efficiency, the evolution grows slightly in Stage I, not as rapidly as shales with low efficiency, and decays in Stage II. The different pore evolution behaviors of these two types of shales are attributed to the contribution of bitumen. However, the evolution of medium–coarse mesopores and macropores (diameter >10 nm) remains flat at high maturation. In addition, high pressure can promote the development of micropores and fine mesopores in highly mature shales.     

Hydrodynamics of oil jets without and with dispersant: Experimental and numerical characterization

In this paper, we present the analysis of an underwater horizontal oil jet experimental measurement and Computational Fluid Dynamics (CFD) using the Reynolds Averaged Navier Stokes (RANS) equations. Two oil subsurface releases were conducted: one with crude oil and another with crude oil premixed with dispersant at the dispersant to oil ratio (DOR) of 1:20. The jet profile was captured by a camera at moderate resolution, and the instantaneous velocity was measured by a Vectrino Profiler. The velocity components, turbulence kinetic energy, and turbulence dissipation rate from the experiment agreed well with those from the CFD simulation using the k-epsilon turbulence model. The spread angle of the jet was found to be around 21° and 24° from the experiment measurement, for oil without dispersant and oil with dispersant, respectively. The latter is close to the angle of miscible jets at 23°. The jet profile of oil with dispersant had a smaller buoyancy than that without dispersant, which is probably due to the large water entrainment for the oil with dispersant jet. The cross sections of the jet for both cases gradually became flattened with distance, as the plume turned upward.     

Distribution and concentrations of petroleum hydrocarbons associated with the BP/Deepwater Horizon Oil Spill,Gulf of Mexico

We examined the geographic extent of petroleum hydrocarbon contamination in sediment, seawater, biota, and seafood during/after the BP/Deepwater Horizon Oil Spill (April 20–July 15, 2010; 28.736667°N, −88.386944°W). TPH, PAHs, and 12 compound classes were examined, particularly C1-benzo(a)anthracenes/chrysenes, C-2-/C-4-phenanthrenes/anthracenes, and C3-naphthalenes. Sediment TPH, PAHs, and all classes peaked near Pensacola, Florida, and Galveston, Texas. Seawater TPH peaked off Pensacola; all of the above classes peaked off the Mississippi River, Louisiana and Galveston. Biota TPH and PAHs peaked near the Mississippi River; C-3 napthalenes peaked near the spill site. Seafood TPH peaked near the spill site, with PAHs and all classes peaking near Pensacola. We recommend that oil concentrations continued to be monitored in these media well after the spill has ceased to assist in defining re-opening dates for fisheries; closures should be maintained until hydrocarbon levels are deemed within appropriate limits.     

Geochemistry and charge history of oils from the Yuqi area of Tarim Basin,NW China

The geochemistry, origin and charge history of oils from the Yuqi area of Tarim Basin have been investigated, through GC, GC-MS and fluid inclusion microthermometry analysis. The Yuqi oils accumulated mainly in three intervals: (1) in the Lower-Middle Ordovician Yingshan Formation (O_1-2y) carbonate reservoirs; (2) in the overlying Upper Triassic Halahatang Formation (T₃h); and (3) in the Lower Cretaceous Yageliemu Formation (K₁y) sandstones. Oils from different reservoirs have distinct physical properties, varying from extra-heavy (O_1-2y), heavy (T₃h), to light oils (T₃h and K₁y). However, their geochemical compositions show a high degree of similarity, which indicates that they derive from the same source rock. Abundant tricyclic terpanes, gammacerane, dibenzothiophene and C₂₁C₂₂steranes, together with a low level of diasteranes, indicate an anoxic marine source rock for oils in the Yuqi area. Oil-oil correlation shows that Yuqi oils derive from the same source bed as Tahe oils. The co-occurrence of intact n-alkanes and 25-norhopanes in all the samples supports the proposition that there is a mixture of an early filled severely biodegraded oil and a late filled fresh oil.In this study, charge history is examined on the basis of integration of fluid inclusion homogenization temperature data with 1D burial-thermal history models. Two episodes of oil charging are identified in the O_1-2y reservoir (well YQX1-1) at around 436-420 Ma (Middle-Late Silurian) and 10-3 Ma (Miocene to Pliocene), respectively. For the samples from the T₃h and K₁y intervals, only one episode of oil charge is indicated by the homogenization temperatures of coexisting aqueous inclusions with an inferred timing around 10-3 Ma. The T₃h heavy oil reservoir is assumed to be a secondary hydrocarbon pool, which accumulated by re-migration and re-distribution of hydrocarbons from O_1-2y hydrocarbon pools. The few early biodegraded oils in the K₁y light oils were probably picked up along the migration pathway during the late fresh oil charging.     

Prediction of hydrocarbon recovery from turbidite sandstones with linked-debrite facies: Numerical flow-simulation studies

A series of two-dimensional numerical flow simulations were carried out to investigate the production characteristics of a sheet sandstone bed with a linked-debrite interval. A deterministic geological model was used based on a two-dimensional representation of a bed from the Marnoso Arenacea Formation. The model was 60 km long and 1 m thick and contained three zones, arranged in a vertical facies arrangement typical of many linked-debrite beds: i) a lower, coarse-to-medium grained, clean turbidite sandstone interval; ii) a middle, muddy sandstone, debrite interval; iii) an upper, fine-grained, clean, laminated sandstone interval. Simulation involved only a 3-km long sector of the model, with one injector well and one production well, placed 1-km apart in the middle of the sector model. The simulated sector was moved progressively down the length of the bed, in 1-km steps, sampling different parts of the bed with different facies proportions. The petrophysical properties of the debrite interval were varied to produce different porosity–permeability cases. All other modelling parameters, including the upper and lower interval petrophysics, were kept constant. Results indicate that, in most cases, key production parameters such as cumulative oil production with time and water cut are proportional to the volume of movable oil between the wells. This relationship does not hold, however, for cases with relatively low values of debrite porosity (≤0.15) and permeability (k_h ≤ 100 mD) where the debrite interval accounts for more than 20% of the interwell volume. In these models, production efficiency declines systematically with reducing reservoir quality and increasing debrite percentage, resulting in relatively low oil production and early water breakthrough.     

钦州湾溢油数值模块及其应用

本文应用水动力模型及溢油模块对代表性风况下钦州湾金鼓江的溢油事故进行情景模拟,且水动力模型结果与实测潮位和实测潮流吻合较好。低潮时发生溢油,不同风况下油粒子在5.5-8.5h后漂到金鼓江上游养殖区。高潮时发生溢油,油粒子在不同风况下漂移轨迹差别较大,例如无风时油粒子在钦州湾颈和三墩外海附近往复运动,而南风3.3m/s工况下油粒子将最终影响大榄坪港区的东南端。另外,高风速下不利风向会缩减油膜抵达敏感区的时间,同时风速越大,蒸发越快。因此风场对溢油模型有重要意义,今后将在精细化WRF模型基础上优化溢油模型并构建溢油决策系统,为地方经济发展和海洋环境保护提供科技支撑。     

Orientation of a pad of SAGD well pairs in an Athabasca point bar deposit affects performance

It has been shown that the performance of a Steam-Assisted Gravity Drainage (SAGD) well pair is affected by its orientation and position within a point bar deposit. In typical commercial operations, multiple horizontal wellpairs, usually arranged parallel to each other, are arranged in pads within oil sands reservoirs. Thus, the overall performance of the recovery process in a point bar is not represented by a single well pair but how the set of well pairs interact with the structure and geometry of the point bar notably including the arrangement of inclined heterolithic strata relative to the SAGD well pairs. This research describes how the point bar structure impacts the performance of a pad of SAGD wellpairs and the impact of pad orientation on performance of the pad. Also, the results show that the variability of the performance of the well pairs within the pad is large and thus, single well pair models do not provide sufficient analysis of the SAGD process performance due to the heterogeneity of the point bar. In other words, pad-scale models are required for recovery process evaluation and design. Furthermore, the variability of performance obtained from the models provides an estimate of the variability that may result for systems where seismic data is not available or is not sufficient to fully characterize the point bar.     

Charging of the Penglai 9-1 oil field,Bohai Bay basin,China: Functions of the delta on accumulating petroleum

The Penglai 9-1 (PL9-1) oil field, which contains China's third largest offshore oil accumulation (in-place reserves greater than 2.28 × 10⁸ ton or 1.49 × 10⁹ bbl), was found in shallow reservoirs (700–1700 m, 2297–5577 ft) within the most active fault zone in east China. The PL9-1 field contains two oil-bearing series, the granite intrusions in Mesozoic (Mz) and both the sandstone reservoirs in Neogene Guantao (Ng) and Neogene Minghuazhen (Nm) Formation. The origins of the PL9-1 field, both in terms of source rock intervals and generative kitchens, were determined by analyzing biomarker distributions for 61 source rock samples and 33 oil samples. The Mesozoic granite intrusions, which hold more than 80% of the oil reserves in the field, were charged in the west by oil generated from the third member (Es₃) of the Shahejie Formation in the Bodong depression. The Neogene reservoirs of the PL9-1 field were charged in the west by oil generated from the third member (Es₃) of the Shahejie Formation in the Bodong depression and in the south by oil generated from the first member (Es₁) of the Shahejie Formation in the Miaoxibei depression. Interactive contact between the large fan delta and the mature source rocks residing in the Es₃ Formation of the Bodong depression resulted in a high expulsion efficiency from the source rocks and rapid oil accumulation in the PL9-1 field, which probably explains how can this large oil field accumulate and preserve within the largest and most active fault zone in east China.