Induced polarization for hydrocarbon exploration: geochemical/geological interpretation

Author(s):  
Dorothy Z. Oehler ◽  
Ben K. Sternberg
Geophysics ◽  
2009 ◽  
Vol 74 (2) ◽  
pp. B47-B59 ◽  
Author(s):  
Paul C. Veeken ◽  
Peter J. Legeydo ◽  
Yuri A. Davidenko ◽  
Elena O. Kudryavceva ◽  
Sergei A. Ivanov ◽  
...  

Delineation of hydrocarbon prospective areas is an important issue in petroleum exploration. The geoelectric method helps to identify attractive areas and reduces the overall drilling risk. For this purpose, induced polarization (IP) effects are mapped caused by the presence of epigenetic pyrite microcrystals in sedimentary rocks. These crystals occur in a shallow halo-shaped mineralogical alteration zone, often overlying a deeper-seated hydrocarbon accumulation. Local enrichment in pyrite results from reducing geochemical conditions below an impermeable layer. The imperfect top seal of the accumulation permits minor amounts of hydrocarbons to escape and migrate through the overlying rocks to shallower levels. During migration, hydro-carbons encounter an impermeable barrier, forming an altera-tion zone. Induced polarization logging and coring in wells confirm this working model. Geoelectric surveying visual-izes anomalies in electric potential difference measured be-tween receiver electrodes. The differentially normalized method (DNME) inverts the registered decay in potential differences, establishing a depth model constrained by seismic and petro-physical data. Diagnostic geoelectric attributes are proposed, giving a better grip on chargeability and resistivity distribution. Acquisition and processing parameters are adjusted to the target depth. Encouraging results are obtained in deeper [Formula: see text] as well as in very shallow water. Onshore, a grounded current transmitter is used. Geoelectric surveys cover different geologic settings with varying target depths. The success ratio for predicting hydrocarbon occurrences is high. So far, 40 successful wells have been drilled in Russia on mapped geoelectric anomalies. Out of 126 wells, the method produced satisfactory results in all but two cases. The technique reduces the risk attached to new hydrocarbon prospects and allows better ranking at a reasonable cost.


Geophysics ◽  
2021 ◽  
pp. 1-47
Author(s):  
Xueyi Jia ◽  
Anatoly Baumstein ◽  
Charlie Jing ◽  
Erik Neumann ◽  
Roel Snieder

Sub-basalt imaging for hydrocarbon exploration faces challenges with the presence of multiple scattering, attenuation and mode-conversion as seismic waves encounter highly heterogeneous and rugose basalt layers. A combination of modern seismic acquisition that can record densely-sampled data, and advanced imaging techniques make imaging through basalt feasible. Yet, the internal multiples, if not properly handled during seismic processing, can be mapped to reservoir layers by conventional imaging methods, misguiding geological interpretation. Traditional internal multiple elimination methods suffer from the requirement of picking horizons of multiple generators and/or a top-down adaptive subtraction process. Marchenko imaging provides an alternative solution to directly remove the artifacts due to internal multiples, without the need of horizon picking or subtraction. In this paper, we present a successful application of direct Marchenko imaging for sub-basalt de-multiple and imaging with an offshore Brazil field dataset. The internal multiples in this example are generated from the seabed and basalt layers, causing severe artifacts in conventional seismic images. We demonstrate that these artifacts are largely suppressed with Marchenko imaging and propose a general work flow for data pre-processing and regularization of marine streamer datasets. We show that horizontally propagating waves can also be reconstructed by the Marchenko method at far offsets.


Geophysics ◽  
2009 ◽  
Vol 74 (4) ◽  
pp. Y7-Y7 ◽  
Author(s):  
Paul C. Veeken ◽  
Peter J. Legeydo ◽  
Yuri A. Davidenko ◽  
Elena O. Kudryavceva ◽  
Sergei A. Ivanov ◽  
...  

Geophysics ◽  
1991 ◽  
Vol 56 (10) ◽  
pp. 1522-1532 ◽  
Author(s):  
Ben K. Sternberg

Our experience with the induced polarization (IP) and resistivity method for hydrocarbon exploration has shown both successful surveys and limitations of the method. Four examples demonstrate a close correlation between shallow IP and resistivity anomalies and deeper hydrocarbon production. In each of these examples, anomalies occurred over the producing fields which have significantly greater amplitudes than the variations in the surrounding background response. Another important result of our research is the development of a geological/geochemical model for the formation of IP and resistivity anomalies over hydrocarbon reservoirs. The two main requirements for formation of IP and resistivity anomalies, according to this model, are: (1) absence of any thick impermeable seals, such as evaporites, above the reservoir and (2) presence of porous, iron‐rich, near‐surface host rocks, such as clastic rock sequences. The IP and resistivity method can be more successfully applied by selecting those areas for surveys in which these two requirements hold. We have also found that the IP/resistivity method for hydrocarbon exploration has significant limitations. Many areas do not appear to have the required geological and geochemical conditions for the formation of IP or resistivity anomalies. IP and resistivity anomalies may also need to be tested with shallow drill holes to separate anomalies caused by hydrocarbon seepage from false anomalies due to other causes.


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