Online Journal for E&P Geoscientists

Akrawi, Karim ^*1; Campagna, Francesco ²; Russo, Lorenzo ²; Yousif, Mohamed Elamin ³; Abdelhafeez, MOh Hassan ³
(1) Research & Development, Geodynamics Worldwide, Abu Dhabi, United Arab Emirates. (2) Research & Development, Geodynamics Research, Rovereto, Italy. (3) Geophysical Ops. Section Technical Services E&P, GNPOC, Khartoum, Sudan.

Surface passive seismic survey is an outstanding technology for Reservoir Hydrocarbon Indicator (RHI) technique to exploration discovery and field reservoir monitoring. It detects the presence of subsurface hydrocarbons fluids in porous reservoirs by recording and spectroscopically analyzing the low-frequency acoustic/seismic background noise (between 0.2- 8 Hz), which is actively emitted by the earth.

The measurements after filtering and analysis can be calibrated with well data and integrated with other geophysical data to provide information which can lower the uncertainty level and minimize risk for exploration drilling and field development decisions.

Measurements survey were carried out in Sudan -Azraq Block with objectives to evaluate their suitability to map the extent of hydrocarbon occurrences in very highly faulted and complex geological situation, in addition to avoid drilling dry wells

The Reservoir Hydrocarbons Indication (RHI) technology applied in exploration areas & field reservoir monitoring.

Geospectra RHI survey technique is based on the principles of non-linear behaviour of fluid systems in porous media. Hydrocarbon in the reservoir pore network can be detected as a characteristic tremor deformation of the natural earth noise spectra in the low frequency range of 0.2 - 8 Hz.

The low sensitive frequency seismic signals are recorded passively at the surface with ultra high sensitive hydrocarbon seismometers. Signals are analyzed based on spectroscopy which produces unique spectral signature anomalies used directly as reservoir hydrocarbon indicator (RHI).

Four advance processing methods been used for this survey includes detailed signal spectrum analysis recorded in time and frequency domains, all four processing approaches confirmed the distribution of hydrocarbon anomaly maps and identified several discovered fields and predicted eight potential prospects.

Areas with hydrocarbons indications are highlighted in the 2D/3D RHI maps and can easily integration with subsurface geological data.

RHI signature is not affected by any structure, stratigraphy or rock types (salt, igneous, clastics, carbonates, faults & etc.), rather it only depend on the presence or absence of hydrocarbons fluids in the porous rock between 1,000 ft up to 16,500 ft.

The survey results in Sudan which cover 300 sq.km with 160 measuring points confirmed the drilling results of 42 drilled wells in six discovery fields and identified eight potential prospects.