Improved Carbonate Reservoir Characterization: A Case Study from a Supergiant Field in Southern of Iraq

Abstract

The objective of this work is to characterize the porosity distribution and the types of carbonate facies in the Mishrif reservoir in the West Qurna/1 Oil Field using seismic inversion results, well log data, rock physics model and core data analysis. Identification of the pore system and the spatial distribution of lithology are keys for constructing Mishrif reservoir model, which have a great impact on the development of the most prolific reservoir in the field Mishrif reservoir. Seismic inversion process is transforming of seismic response into a quantitative elastic properties of the reservoir rocks. It enables the modeling of porosity and lithology distribution in 3D space away from well control. In order to achieve the aim of the work, a step wise approach will be taken. First of all, the vertical distribution of porosity based on well log data and its relationship with elastic properties was undertaken. A model-based seismic inversion guided by rock physic analysis modeling was applied across the high resolution 3-D seismic data, and integrated with core data for validating at Mishrif intervals. The porosity volume was then generated over the entire West Qurna/1 field based on the linear-regression analysis. The interpretation of seismically derived characterization in the Mishrif reservoir observed a different lateral distribution of acoustic impedance. The results were correlated with computed acoustic impedance log and core analysis data to classify lithofacies of the Mishrif interval. The resulting porosity volume was validated with well log data where good consistency was indicated. By slicing through the porosity volume, it shows a high porosity in many carbonate features with low acoustic impedance which reflect a good reservoir quality (grainstone tidal channel or the accumulation of corals and mounds facies). This observation implied that Mishrif zones displayed a wide range of porosity and lithology fluctuations due to the impact of depositional environment. The workflow provided insight into the porosity distribution and quantification of its influence on dynamic reservoir behavior. The estimation of the porosity based on seismic data, can increase the reliability of reservoir characteristics through providing a more detailed of porosity distribution in interwell regions. Overall, this study will ultimately lead to improve the development plan of wells in terms of production performance, and economic value of the West Qurna/1 oil field and similar heterogeneous carbonate reservoirs.

Structure Analysis of Sa’adi Reservoir in X Supergiant Oilfield, Southern Iraq

“…This process can be achieved by using a Time -Depth Relationship from chock shot or VSPs to calibrate the sonic logs [8]. In this study, Seismic to Well Tie (SWT) was done for seven wells inside the study area.…”

Identification method of thief zones in carbonate reservoirs based on the combination of static and dynamic data: A case study from the Cretaceous Mishrif Formation in the H oilfield, Iraq

“…The high reservoir heterogeneity of the Mishrif Formation in the H oilfield is usually caused by the comprehensive influence of the sedimentary environment, diagenesis, tectonics, etc. (Ghafoori et al, 2009;He et al, 2014;Al-Ali et al, 2019). There are various lithofacies (with different particle types, particle contents, pore structures, and physical properties) that develop when sedimentary environments change.…”

“…Carbonate reservoirs play an essential role in oil and gas recovery, especially in the Middle East and Middle Asia (Liu et al, 2016). Generally, there is a strong heterogeneity in carbonate reservoirs due to the comprehensive impacts of tectonic movement and the leaching effect (Ghafoori et al, 2009;He et al, 2014;Al-Ali et al, 2019). During oil and gas recovery, the zones with relatively high permeability will form low-resistivity seepage channels of fluids, that is, the so-called thief zones (Fu et al, 2019).…”

Structural Geometry Analysis of Khasib Formation in West Qurna I and II Supergiant Oilfields, Southern Iraq

“…For example, errors resulting from miss calibration of the acoustic log, tend to be accumulated when the log is running over numerous thousands of meters (Bacon, 2007). Therefore, the acoustic log is generally calibrated with a time-depth relationship from VSP or check-shot before combining with the density log to produce acoustic impedance (Al-Ali, 2019). Finally, the synthetic seismogram is generated by convolving the reflection coefficients spikes using well log data with the wavelet extracted from the seismic data.…”