OFFSHORE NAMIBIA Thermal history reconstruction based on AFTA and VR data.

Non-exclusive study

Namibia's offshore area overlies a series of Mesozoic and Tertiary sedimentary basins that are virtually unexplored by drilling. To date only seven exploration wells have been drilled, the first discovering substantial gas reserves at the Kudu field now undergoing development. The area holds considerable exploration potential and all open acreage will be offered for licensing in the 3rd Licensing Round, which opens on 1st October 1998.

The recognition of marine oil-prone source rocks in the Cretaceous gives the area significant oil potential. Their maturation and hydrocarbon generation histories are however a critical exploration risk factor.

The distribution of maturity will depend critically on the relative affects of paleothermal episodes, due for example to deeper burial prior to uplift and erosion, heat flow variation or the effects fluid movement. Recognition of such episodes and measurement of both their timing and affects in terms of maturity development are therefore a vital part of prospectivity assessment. This study will, for the first time, provide reliable data on these important aspects of the evaluation of offshore Namibia .

Aims and objectives

The project aims to investigate these problems by direct assessment of the timing and magnitude of paleo-thermal effects in wells from the offshore region. Rather than relying on theoretical models, use of AFTA and VR data will allow direct measurement of the paleo-thermal episodes responsible for maturity development and hydrocarbon generation.

Specific objectives include:

• identification of the major thermal episodes affecting the drilled section
• quantification of the timing and magnitude of maximum paleotemperatures
• characterisation of the processes responsible for each episode
• measurement of paleogeothermal gradients
• quantitative assessment of timing of maturation of source rock horizons
• estimation of the timing and amount of uplift and erosion at each studied location
• recognition of any non-burial related thermal effects, caused for example by heat flow variation
  or fluid movement
• regional synthesis of thermal history including history of maturity development and regional
   variation in timing of peak hydrocarbon generation, discussion of implications for oil and gas
   generation.

Work program

The project is based on 15 new AFTA and 27 new VR analyses from wells Kudu 9A-3, 2213/6-1 and 2012/13-1 and on published information from the Kudu 9A-2 well and two DSDP sites.

Deliverables

Comprehensive report containing full details of AFTA and VR data interpretation and a regional synthesis including discussion of implications for hydrocarbon prospectivity. All AFTA and VR data plus supporting geological information, together with discussion of analytical details will be presented. Results will be presented in an Executive Summary with accompanying summary diagrams and tables. Discussion of data quality will also be provided.

Supported by NATIONAL PETROLEUM CORPORATION OF NAMIBIA (NAMCOR)

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