ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1965.tb01946.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1965.tb01947.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

ABSTRACTWhereas the first success of petroleum exploration in France (the gas deposit in the St. Marcet anticline in the St. Gaudens region) was essentially based on geological surveys, the second (the Lacq field in the Pau region) was the fruit of reflection shooting. In fact, the Lacq anticline cannot be detected by surface geology because of the Quaternary and Tertiary cover. Besides, electric and telluric prospecting methods could not be used over this zone as an electrified railway line passes through it.As stated then, it was the reflection shooting method that revealed the Lacq structure in 1948, during a reconnaissance survey conducted by Compagnie Générate de Géophysique using a very simple technique (only one geophone per trace).By the seismic technique of 1948, quite good reflections were obtained from a level adjacent to the top Cretaceous, but only sporadic reflections were picked up from a deep level and then only on the flanks of the structure, except for the southern one where results were nil.Towards the end of 1949, the first well, La 1, using a heavy rig designed to reach deep layers, led to the unexpected discovery of the upper oil deposit at a depth of 600 m in the Upper Cretaceous (lower Senonian), while the third well, La 3, led to the discovery by blow‐out of the lower gas accumulation at a depth of 3,500 m in beds later identified as lowermost Cretaceous and, more particularly, Upper Jurassic (Purbeckian).As no great geophysical effort was called for, the upper oil deposit was rapidly developed, its depth and dimensions being modest (6 km2).As far as the deeper gas deposit is concerned, the main objective up to 1954 was to gain a picture of the central part of the anticline. Despite the use of a more detailed seismic technique, it was difficult to plot the top of the structure at the level of the uppermost Jurassic. From 1952 to 1957 the wells La 101, La 102, La 103, La 104, La 105, La 106 and La 113 were drilled, which made it possible to evaluate the gas reserves.Then began the wide‐scale and systematic exploration of the structure, by drilling on the one hand and by reflection shooting on the other. Profiles were shot perpendicular to the axis, but long enough (20 to 30 km) to cover the entire anticline (seismic surveys of 1956–57–58).The eastern pericline and the northern flank were quite easily plotted by seismic survey at the level of the top Jurassic, whereas the southern flank, which has a distinctly steeper slope than the northern one, could not be traced very far–so that the problem of the relationship between the uncomplicated structure of Lacq and the country to the south, with its complex, deep tectonics, still remains an open question.The western pericline, however, remained a subject of concern. Its relationship to the anticline of Ste. Suzanne (outcropping Jurassic) was a mystery.In 1956–57 the well SV 101 confirmed the hypothesis of an overthrust which, without affecting the anticline of Lacq, borders it to the south and west. The thrust is not very large in the south (Lagor wells) but assumes considerable proportions in the west: the Ste. Suzanne anticline actually forms part of a thrust from the south, about 5, 000 to 6, 000 m thick, as the exploration of the region by reflection shooting and drilling (SSE 101, OR 102) has shown. This exploration had been undertaken in search of a new structure under the thrust that might form an extension of the Lacq structure.In 1959 a detailed gravimetric survey (2 to 3 st./km2) was carried out in the Lacq region because the old survey map (1948–1 station/8 km2) had proved progressively inadequate for interpreting the seismic data. It was found that the structure of Lacq had only a small anomaly in comparison with its dimensions. This surprising phenomenon is still difficult to explain. Are the surfaces of equal specific gravity independent of the stratigraphic planes, or has the effect of the anticlinal roof of the Cretaceous and the Jurassic been balanced by that of a saliferous and intumescent Triassic right in the core of the structure?The small anomaly which it was possible to detect may be explained by a thick sequence of reef limestones in the centre of the anticline on the Lower Cretaceous, as indicated by drilling results. These severely fissured limestones are undoubtedly partly to blame for the bad seismic results obtained on the central part of the structure as far as the deep horizon, adjacent to the top Jurassic, is concerned. They are also responsible for the considerable anomalies in the velocity of seismic

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1965.tb01948.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

ABSTRACTThis new method of calculation, of the second vertical derivative of gravity or magnetic fields is appreciably different from the classical methods because it is based upon the variations of the distance between the isogams rather than a regular grid with “constant spacing”. In a certain way, it is a method of “constant interval”. A number of practical advantages are inherent to the method, among these, the possibility to use the cartesian charts with bi‐logarithmic scales which make the calculation much easier, and the creating of iso‐error maps which are indispensable for the interpretation of the derivative maps. Three examples of practical application are given, two of them pertain to gravimetry, the third to aeromagnetism. These results are compared with second derivative maps obtained with ot

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1965.tb01949.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

ABSTRACTIn this paper direct interpretation methods of resistivity observations are discussed, which use the kernel function in the integral expression for the potential as an intermediary step. This kernel function can be expressed in the form of an integral expression, involving in the integrand a Bessel function and the apparent resistivity. This expression is the basis for the determination of the kernel function from the apparent resistivity curve. The integral can be determined directly; this method of computation, however, although practically feasible, is rather time consuming. Another method of computation is to approximate to the resistivity curve by a sum of a small number of two‐layer curves which are asymptotic to the observed resistivity curve. This method, which was described in a previous paper by the present author, is briefly restated. A more general method is to approximate to the observed resistivity curve by a sum of functions of other types; the choice of such functions is only restricted by the requirement that the contribution to the kernel function corresponding to them should be easily computable. Two different types of functions, that satisfy this condition, are discussed. The standard curves required for the application of the method are presented. An example of application of the method is given.The problem of determining the resistivity stratification from the kernel function has been solved by Pekeris in 1940. The method of Pekeris is briefly restate

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1965.tb01950.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

ABSTRACTAfter a brief reference to the various possibilities of measuring induced polarization, the experimental setup of a transistorized earth resistance meter is shown which allows one to measure the (real) resistance at the frequencies 9 cps and 1.5 cps. As a measure of the induced polarization, it supplies directly the resistivity percentage difference. The possibilities of its use are explained in detail and further development is considered.

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1965.tb01951.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

ABSTRACTThe method of induced polarization finds more and more application in the prospection of metallic ore deposits. It is very useful also in the determination of non‐metallic minerals and underground water flows.In the case when an electrical current flows accross the interface between metallic and electrolytic phases the causes of the induced polarization are well known and have often been discussed. In the case of non‐metallic minerals and rocks the polarization is mainly caused by the membrane potential, since the polyelectrolytic clay material, having the capacity of ion‐exchange in micells, acts as a semipermeable membrane.Practical examples of exploration for non‐metallic mineral by the induced polarization method are discussed. Some kaolin deposits have been revealed. The depth and the extent of a clay layer, impervious to water, are determined in the bottom of a future storage lake of an hydroelectric power‐plant. The underground water flows in the Karst region a

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1965.tb01952.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

ABSTRACTA description and classification is given for those later events in seismograms of refraction–and wide angle reflection shooting which travel nearly parallel and at constant time intervals behind the first arrivals and which are frequently observed in field surveys. Multiple events with the velocityV1of the uppermost layer may be caused by multipleP‐reflections and certain velocity conditions or byPS‐conversions. In addition to these types multiple events with the velocityV2orVnmay be caused by reflected refractions or by reflected diving waves. The different types will be distinguished mainly by means of travel time–and amplitude‐consi

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1965.tb01953.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

ABSTRACTThe headwave system for an incidentP‐wave in a two‐layer case has been traced in the ‘inside’ of a two‐dimensional model and it is found that the measured fronts do not coincide with the wavefronts constructed according to the Huygen's principle. A refraction profile indicates different velocities near the critical distance but shows the true value for the higher velocity medium at greater distances. An error in the intercept time, which is about 6 % too high in the example, should, however, always be present even if extrapolation is done from the region where the profile shows the true velocity of t

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1965.tb01954.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

Book reviewed in this article:E. I. HamiltonApplied GeochronologySolar System Radio Astronomy, edited by Jules AaronsMarySears, Progress in OceanographyClays and Clay Minerals, edited by W. F. Bradley, Proceedings of the Twelfth National Conference, Monograph No. 19, Earth Science Series.

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1965.tb01955.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY