Hi-resolution electrical acquisition for oil and gas prospecting.
Complex innovative geophysical enterprise " SOLITON " is formed by professional geophysicists in YUZHMORGEO Association, further the same team at YUZHMORNEFTEGEOFIZIKA Trust for the organization and carrying out of sea, ground and well-ground geology-geophysical works at the decision of problems of searches and investigations of deposits of minerals, engineering-geological and hydro-geological researches.
The basic directions of works of the enterprise are: - Search of oil fields and gas in any environment - the seas, the rivers, estuaries, a land - mountains, deserts and so forth, with application of a complex of methods, basically on the original technologies developed by experts of the enterprise. Application of new original technologies allows to raise essentially quality of the forecast, at essential reduction in price of works.
The technology allows to apply simultaneously three independent electroprospecting methods: 1. The Standard method of the Caused polarization (IP), allowing to receive the information on presence or absence of deposit УВ by way of, without a binding on depth. THEORETICAL AND EXPERIMENTAL FOUNDAMENTAL OF HREP
Effects of the double induction polarization (DIP) and secondary seismoelectrical one (SSEF) opened by authors during researches under grants of the RFFI lay in a basis of high-resolving electrical prospecting (HREP).
Extensive experimental materials have shown, that process of becoming is accompanied, at least, by two kinds oscillatings: rather low-by frequency type (0.2 - 2 Hz), spreading in time, and more high-frequency type (2 - 120 Hz) with practical preservation of frequency for all time of registration.
Mathematics characteristic of DIP is represented in integrals of convolution of the transient field characteristic above not polarized medium and the dependence from the induction polarization of specific resistance of layers in time.
Secondary Seismoelectric effect SSEF is caused by transformation known the return seismoelectrical the effect arising due to change of an electric field in time, in known direct Seismoelectric effect, especially strong on borders so-called "formation objects", i.e. on borders of sedimentation breaks.
APPLICATION OF HREP FOR SEPARATE FORECAST OF OIL AND GAS DEPOSITS
The estimation of resolution of time geoelectrical sections is given in comparison with the seismic time sections of seismic CMP, fulfilled in various geologo-geophysical conditions in different regions of the world (fig. 1, 4, 5, 6, 10, 11, 12, 13, 14). From the resulted materials it is following rather quite good concurrence of seismic and geoelectrical sections. Other important factor of this technology is the opportunity of the separate forecast of hydrocarbons (Fig. 1-8, 10-15).
Oil deposits are precisely enough marked by raised anomalies of IP However in the mentioned researches the results, which are not conterminous with accepted representations on display of hydrocarbon deposits in an induction polarization field, were often enough marked. In some cases above the revealed traps for oil and gas or above known deposits anomalies of IP parameter showed the steady tendency to reduction concerning a background. It has been established, that such behavior of IP parameter usually occurs, when hydrocarbon deposit is presented only in the form of natural gas (a fig. 4, 5, 6). Thus it is possible to speak about the forecast of character of hydrocarbonic saturation for a layer: increase in values of parameter IP speaks about presence of oil, and reduction in values of IP parameter concerning a background characterizes gas deposits.
Results of HREP, executed within the limits of known according to acoustics and ground extraction gas-hidrad deposit in area of Kerchensky-Tamansky shelf, are rather indicative. Feature of the given works were essential depths of the sea from 500 up to 1 600 m. Basically, it was the opportunity in practice to estimate technology of the high resolution on ideal test area: in fact the first water layer represents rather low-resistance, practically with the zero polarizability, the homogeneous horizon essentially enough changing its thickness within the limits of a site of works.
Data of TEM-DIP methods show following 1. The layer of water is rather precisely marked on TEM-DIP sections. This layer is marked by essentially lower values of polarizability at rather high degree of uniformity of values, in comparison with the rocks lying below the bottom. Comparison of behavior character of the allocated first layer with behavior character of the bottom, certain both from a sea chart, and from potential difference values, on early times, shows good enough correlation on all four fulfilled sections. Thus, the next proof of competency of the recommended before approach to electrical prospecting methods is received.
2. On TEM-DIP sections the object of the raised polarizability is with a different degree of confidence marked, that coincides on surface and depth with the gas-hydrate deposit certain earlier according to acoustics and ground extraction. Thus, it is shown, that offered technology TEM-DIP works for this problem.
RESULTS OF HREP IN THE PACIFIC The next tests of technology opportunities are lead in the Pacific, to the north from the Taiwan island on three profiles in length everyone about 70km. According to the classical IP method the anomalies of IP parameter are received, that coincide with the basic traps allocated according to seismic CMP. In a zone of crossing of all three profiles the anomaly of IP parameter is confidently contoured (Fig. 9). Character of anomalies of IP parameter with steady tendency to reduction of values concerning the background has allowed to make the forecast about presence mainly of natural gas deposits in the investigated territory.
It is interesting to note also rather quite good concurrence of seismic and geoelectrical time sections (Fig. 10- 12). It is marked rather quite good concurrence in behavior of borders. It is possible to note also allocation of the local raised block in area of pickets 760 - 770 on the profile 3 in geoelectrical section. To this block there corresponds the similar block on seismic section.
The anomalous DIP objects according to TEM-DIP data are allocated, that in plane coincide with the IP results given above. On TEM-DIP sections in area of crossing of the profiles1, 2 and 3 there are two anomalies DIP on depths accordingly 2 200 and 2500m nearby. Concurrence of the data for three independent methods: anomalies of IP parameter, without a positioning on depth, anomalies of DIP parameter, with a positioning on depth, zones of possible traps - anticlinal inflections according to geoelectrical time sections SSEEF - raises essentially reliability of the forecast of oil and gas deposits.
ADDRESS FOR CONTACTS:
2. "Know-how" technology DIP or IIP, allowing to receive the information on presence of deposit УВ, with a binding on depth. ( patents N93041480 G01V3/08 from August, 16th, 1993 and №67731 from July, 2nd, 2007. Authors: Nebrat A.G., Sochelnikov V.V.)
3. "Know-how" technology VSSEEV, allowing to receive time geoelectric cuts with a high degree of the sanction, practically at a level of seismic prospecting seismic (the Patent № 67732 from July, 26th, 2007. Authors: Nebrat A.G., Sochelnikov V.V)
From the point of view of the lead theoretical researches low-frequency oscillations are caused by effect DIP, and high-frequency - by SSEF effect. The method of high-resolution electrical prospecting including complex TEM-DIP- SSEF is patented.
The physical essence of effect DIP consists in the following. As a result of transient process the electric field in the conductive medium after switching a source on or off changes not sharply, and smoothly. The more depth of layer, the there come changes later. There is an additional source of the induction polarization that leads to its change which in the beginning grows on absolute size, and then in process of attenuation of the additional source decreases. So there is the double induction polarization DIP. And, the more depth of a polarized layer, the on later times it will be shown this layer in the DIP field.
Estimations of size of the electric field intensity created by these charges, are in good conformity with practical results of measurements.
By means of the second kind oscillations it is possible to receive time geoelectrical sections possessing a lot of attractive properties for application in geophysics: it is small speed of distribution - 300 - 500м/сек., absence of multiple waves, rather small decrement of attenuation. It is theoretically shown, that the amplitude of a signal is proportional to porosity, also there is a dependence of a signal on permeability.
( look at appendix 14, 15, 16)
Anomalies of DIP parameter are located:
on profile 1 - pickets 360-418 Fig.10,
on profile 2 - pickets 290-340 Fig.11,,
on profile 3 - pickets 210 - 280 Fig.12.
A well drilled subsequently in a zone of crossing of the profiles 1, 2 and 3 has shown presence of a deposit of natural gas in an interval 2270-2290m and oil in an interval 2510-2530m. Thus the data of drilling have once again confirmed the results received by means of TEM-DIP technique. Positive results are received in enough uneasy situation: greater depths of the sea 150-200m, rather the greater depths of objects divided at depth more of 2200m of all on 230m. These data allow to make conclusion about enough high opportunities of TEM-DIP technique under the forecast of oil and gas deposits with their positioning on depth.
Thus, on the basis of the given data, essentially wider application of a complex of highly effective, highly productive and little cost IP, DIP and SSEEF methods, allowing to give a prognosis estimation of presence or absence of oil and gas deposits, including the forecast of fluid- saturation character, is recommended.
Mr. Alexandr G.Nebrat
SOLITON
38, Krasnogvardeiskaya Str., Gelendzhik, 353470, Russia
Phone: ( 86-141) 5–38-14,
8-918-440-7281 or 8 961–510-8962
E-mail: 
