A review of basic well log interpretation techniques in highly deviated wells

Drilling deviated wells has become customary in recent times. This work condenses various highly deviated and horizontal well log interpretation techniques supported by field examples. Compared to that in vertical wells, log interpretation in highly deviated wells is complex because the readings are affected not only by the host bed but also the adjacent beds and additional wellbore-related issues. However, understanding the potential pitfalls and combining information from multiple logs can address some of the challenges. For example, a non-azimuthally focused gamma ray logging while drilling (LWD) tool, used in combination with azimuthally focused density and neutron porosity tools, can accurately tell if an adjacent approaching bed is overlying or underlying. Moreover, resistivity logs in horizontal wells are effective in detecting the presence of adjacent beds. Although the horns associated with resistivity measurements in highly deviated wells are unwanted, their sizes can provide important clues about the angle of the borehole with respect to the intersecting beds. Inversion of horizontal/deviated well logs can also help determine true formation resistivities. Additionally, observed disagreement between resistivity readings with nuclear magnetic resonance (NMR) T2 hydrocarbon peaks can indicate the presence or absence of hydrocarbons. Furthermore, variations in pulsed neutron capture cross sections along horizontal wells, measured while injecting various fluids, can indicate high porosity/permeability unperforated productive zones. Finally, great advances have been made in the direction of the bed geometry determination and geologic modeling using the mentioned deviated well logs. More attention is required toward quantitative log interpretation in horizontal/high angle wells for determining the amount of hydrocarbons in place.

METHODS OF OIL SATURATION MODELING AND THEIR APPLICATION IN IRAP RMS

Одним из важнейших свойств залежи является нефтенасыщенность. При моделировании распределение нефтенасыщенности является одним из основных параметров для подсчета запасов и дальнейшего гидродинамического моделирования. В статье рассмотрены варианты построения куба нефтенасыщенности с учетом априорной информации в виде данных результатов интерпретации геофизических исследований скважины, капилляриметрических испытаний и 3Д-трендов, а также алгоритмы реализации описанных методов в программной среде IRAP RMS. Построены геологические модели по описанным методам. Proper distribution of oil content is one of the main parameters for reserves assessment and further flow simulation. The paper reveals the variety of approaches to oil saturation cube building based on well log interpretation data, capillarimetry and 3D-trends and also the algorithms of the realization of these methods in reservoir modeling software IRAP RMS. Geological models are built using the described approaches.

Stratigraphic analysis and calculation of reserves in the Colorado field, MMV, Colombia

Based on review of previous information and correlation of 7 lithostratigraphic sections from well data, it was possible to establish the presence of channels in fluvial environments of the Mugrosa Formation, with good lateral continuity, in the B and C zones, in the Middle Magdalena Valley Basin (VMM). The results of well log interpretation (NSP logs) indicate the presence of channel sands and proved the previous sedimentological model of the field. In the sedimentological model proposed, zones B and C (Mugrosa Formation) show a very good lateral continuity of sands. The reserve calculations of original oil in place (OOIP) and original gas in place (GOES) indicates that the largest reserves of oil and gas are located in the zone C, with reserves of 118 million bbl and 33.9 Gigas of cubic feet respectively.