FAULT TECTONICS OF THE NE BLACK SEA SHELF

AND ITS RELEVANCE TO HYDROCARBON POTENTIAL

BERAN GÜRLEME - 2014 - KOCAELİ

INTRODUCTION

Faults of the consolidated crust play crucial role in the origin of sedimentary features andhydrocarbon accumulation in them. However, their setting is unknown on the NE Black Seashelf.

INTRODUCTION

Therefore, the aim of this study is as follows:● to first compile a map of faults in the consolidated crust

applying an innovative approach● to interpreting gravity and magnetic data;● to analyzeinfluence of crustalfaults on the formation of

sedimentaryfeatures;● to test alinkagebetweencrustaldisturbances and

potentialhydrocarbonfeatures;

INTRODUCTION● to examine relationship between gas seeps and fault

tectonics;● to determine the thermal and stratigraphic position for

zones of oil anad gas origin.

Understanding these factors may be helpful in planning location of exploration holes.

LOCAL UPLIFTS ON THE NORTH-EASTERN SHELF OF THE BLACK SEA

A multi-channel seismic surveyresulted in the discovery of about20 local uplifts in the Paleogeneand Neogene oil and asbearingsequences of the region .Mass media in Ukraine report thatthe Subbotina feature is an oil field.Drilling of holes is inprogress todetermine its reserve.

Scale 1:1 200,000Contour interval is 2.5 nTContour interval is 2 mGal

3D STRUCTURAL MODEL & LAYERSDENSITY FOR SEDIMENTARY COVER

(a) Sea bottom topography(b) Depth to the top of the Maikop series(c) Depth to the bottom of the Maikop series(d) Depth to the top of the Upper Cretaceous layer(e) Depth to the top of the consolidated crustDensity is in g cm3.(a) Water ( 1.03);(b) Pliocene –Quaternary sediments (1.87-2.17)(c) Maikop series (2.34);(d) Eocene-Paleogene (2.57);(e) Cretaceous (2.64); Data for density values are from (Starostenko et al., 2003).

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COMBINED GRAVITY EFFECT OF WATER AND SEDIMENTARY LAYERS

A total gravity effect of water,sedimentary cover and mantle wascalculated to discriminate the crustalcomponent of the observed field.Most sedimentary features aremarked by negative anomalies(e.g.Subbotina, Moriana, Abikha) or arelocated in the gradient zones (e.g.Palasa, Dreifova, Yakorna,. The Kerch,Sokolova, NE Moriana) features areregistered by positive anomalies oflow intensity.

RESIDUAL GRAVITY FIELD & ELEMENTS OF ITS

DISTORTIONS IDENTIFIED AS FRAGMENTS OF FAULTS

The residual gravity component ofthe consolidated crust was obtainedby removing the combined gravityeffect from the observed field.The horizontal-gradient method wasused to discern steep gradientsTheyare identified as fragments of faultsand shown by straight lines in .black.Most sedimentary features arelocated in the gradient zones.

LOCAL COMPONENT OF THE GEOMAGNETIC FIELD AND ELEMENTS OF ITS DISTORTIONS IDENTIFIED AS FRAGMENTS OF FAULTS

The local component was obtained byremoving the regional field from theobserved field. The horizontal-gradientmethod was also used to discern steepgradients.The steep gradients are identified as thefragments of faults and shown by straightlines in red.

Threelargezones of thefaults are recognized:the Uzurlasko-Gornostaivskazone with NE strikehas a width of ca.7km(1);the Pravdynska zone with N E strikehas a width of 10-20 km (2);the Molbaiskazone with NW strikehas a width of 10-15 km (3).The strike of the faults at the bottom of thePaleogenelayeriscontrolled by the diagonalsystem. It implies that younger faults inherited theolder tectonic pattern

FAULTS OF THE CONSOLIDATED CRUST

REGIONAL RESIDUAL GRAVITY FIELD OF THE SEDIMENTARY COVER

3-D regional model was obtained to discernthe regional peculiarities of the fault tectonicsand its relationship with the gradient zones.Only the Blagodarna, Dreifova, Palasa andNW P. Kerchenska features are located in thegradient zones. The rest of the features areundoubtedly situated within the blockbounded by the steep gradients of theresidual gravity field.

Its name is the Mithridatesblock.

GAS SEEPS AND SUBMARINE CANYONS

INFORMATION 1. Over 75% of theworld's hydrocarbon basins containsurface seeps

INFORMATION 2. The gasreserves in the sediments ofa the Nilefan are estimated to be 80 trillion m3

GAS SEEPS AND AND ABNORMALLY GAS-SATURATED DEPOSITS

Contours of gas-satu rated deposits are from Shimcus et .al.,1998. The gas (methane)content is 0.1-1.0 ml per 1 kg of sediment.

gas seeps;submarine canyons;isobaths, m;gas (methane) in deposits;tectonic faults;neotectonic disruptions

CRUSTAL FAULTS, GAS SEEPS AND ABNORMALLY GAS SATURATED DEPOSITS

Gas seeps and abnormally gassaturated deposits are localized in thezones of the deep gradient, crustalfaults of NE and the EW strike as wellas within the buried Don fan.Collectively these observations allowus to recommend the belt on the uppercontinental slope as a new potentialhydrocarbon area.

Gas (methane) in deposits

Gas seeps

THERMAL EVOLUTION OF THE PALEOGENE AND NEOGENE SEQUENCES

Based on the temperature-time indices (TTI) in the Mithridates block, the mostfavourable conditions for oil generation are in the Upper Eocene and LowerMaikop sequences. These calculations are supported by a presence of oil in coresamples of similar age from the Subbotina feature. As for gas, it can be mostlygenerated in the UpperCretaceous and Eocene sediments.

MAJOR CONCLUSIONS● For the first timethereisamap of faults at a scale of 1:200,000 for the

consolidated crust on the northeastern shelf of the Black Sea;● tectonic distortions in the sedimentary layers are controlled by the faults in

theconsolidated crust;● all potentially hydrocarbon uplifts are localized within the Mithridates

autonomous block at the junctions of the faults of the different orders withthe northeastern and sublatitudinal strikes;

● the faults serve as channels of vertical-migratinghydrocarbon;● the zone on the uppermost continental slope is recommended as a new large

hydrocarbon prospective area;● due to the thermal regime in the Mithridates block, the Upper Eocene and

Maikop sequencesarefavourable for oil generationwhile the Eoceneand theUpper Cretaceous — for gas generation.