Utility and integration of Non Seismic data in Kurdistan

Mumaw, Gary Robert (Senergy Ltd)

OnePetro 

The increasing complexity of new exploration targets requires the use of both seismic and non-seismic methods in the exploration process. This is readily achieved by integrated workstation software that enables simultaneous interpretation and modelling of both data sets. Where 2D seismic control is sparse and highly ambiguous, Gravity and Magnetic data provide additional independent measurement of the subsurface; and a more reliable integrated interpretation of complex geologic structure, adding value and reducing risk. Further, continuous improvement in data resolution and sensitivity [from land, marine and airborne acquisition and processing systems] are making completely new applications possible, expanding Potential Fields methods from regional ‘reconnaissance' tools into prospect scale and to some extent, reservoir scale, including both 3D full tensor gravity (3D-FTG) and magnetic gradiometry technology. Unfortunately, turmoil in the region has prevented their airborne survey deployment to date but this could readily change with improving political stability in Iraq-Kurdistan. Meanwhile, high quality public domain regional space mission ‘satellite derived' gravity and magnetic data provides the focus for understanding and mapping the tectonic framework: basement architecture and distribution of igneous bodies. Structural information so derived can be combined with basement depth estimation to improve understanding of basin morphology, evolution and the petroleum system. It can also prove valuable in identifying continuity between well and seismic data. This paper demonstrates the utility and integration of regional scale public domain non seismic data to assist with the local scale structural model and prospectivity assessments of some high fold zone blocks of interest in NE Iraq/Kurdistan. The Bazian (Block) anticline is used to illustrate a typical local scale feature for evaluation.

Introduction:

The Kurdish Regional Government (KRG) controlled parts of Iraqi Kurdistan are estimated to contain around 40 Billion barrels of oil and 60 TCF of gas (14USGS) making it the sixth largest petroleum reserve in the world. Sparce 2D Seismic control using both dynamite and vibroseis source are the primary geophysical data set for subsurface evaluation. Further, these often widely spaced data are highly variable in S/N exhibiting discontinuous reflection character and highly ambiguous subsurface geometries on the Post Stack Time Migrated (PSTM) section, particularly over rugged terrain. Thus, a valid geologic structural model is critical to the 2D seismic interpretation process. Public domain space mission-satellite derived regional topography, gravity and [to a limited extent in this case] magnetic data is used to help identify and delineate structural fabric, lineaments and basement block configuration in relation to both regional and local block prospectivity assessment in the low [foothills] and the high fold zones of Kurdistan. Often when the seismic data lacks the penetration capability or the spatial coverage, these data provide an independent data set to image the regional scale deep basement structure and fault trends critical to understanding, validating and evolving the imposed structural model. Both thin and thick skin detachment deformation are often valid models to explain crustal shortening and fold [trap] formation in the Zagros. Data integration at local scale was achived via a 2D seismic survey that was interpreted in conjunction with this work. Although some local scale ground survey data [gravity and magnetic] is available throughout the Low [foothills] Fold Zone (LFZ), no local scale data exists in the High Fold Zone (HFZ) of interest. This is thought due to difficult terrain in the HFZ. The Bazian (block) anticline illustrates local scale context/detail for the regional data in the HFZ. Figure 1 shows the two principal structural domains of interest in Kurdistan. Although this study is limited to public domain regional scale data(figure 2), high resolution local scale airborne gravity gradiometry could readily be deployed in this area but is currently restricted in terms of no-fly zones, e.g., 13US ITAR regulations. A sensitivity study to determine density contrast issues of the geologic targets is required to assure a useful data set.