Pre-stack inversion for caved carbonate reservoir prediction: A case study from Tarim Basin, China

Abstract

The major storage space types in the carbonate reservoir in the Ordovician in the TZ45 area are secondary dissolution caves. For the prediction of caved carbonate reservoir, post-stack methods are commonly used in the oilfi eld at present since pre-stack inversion is always limited by poor seismic data quality and insuffi cient logging data. In this paper, based on amplitude preserved seismic data processing and rock-physics analysis, pre-stack inversion is employed to predict the caved carbonate reservoir in TZ45 area by seriously controlling the quality of inversion procedures. These procedures mainly include angle-gather conversion, partial stack, wavelet estimation, low-frequency model building and inversion residual analysis. The amplitude-preserved data processing method can achieve high quality data based on the principle that they are very consistent with the synthetics. Besides, the foundation of pre-stack inversion and reservoir prediction criterion can be established by the connection between reservoir property and seismic refl ection through rock-physics analysis. Finally, the inversion result is consistent with drilling wells in most cases. It is concluded that integrated with amplitude-preserved processing and rock-physics, pre-stack inversion can be effectively applied in the caved carbonate reservoir prediction.

An Amplitude-Based Modeling Method and its Application on the Impedance Inversion in Heterogeneous Paleokarst Carbonate Reservoirs

“…Significantly, the basic criterion for preserving amplitude is that the AVO characteristics between synthetic and obtained gathers should be similar (Sun et al, 2011;Zhang et al, 2011a;Zhang et al, 2011b;Feng et al, 2012). Meanwhile, the pre-stack seismic inversion should be carefully applied by seriously controlling the quality of four major approaches, including angle partial stack data preparation, wavelet estimation, low-frequency model building and inversion parameter control (Zhang et al, 2011a;Zhang et al, 2011b). Theoretically, the pure P-wave data are prone to be more precisely achieved than other elastic www.ccsenet.org/esr Earth Science Research Vol.…”

“…On the contrary, a more reasonable AI LFM considerably preserved the heterogeneous reservoir information (Figure 7b) has been successfully constructed by the proposed amplitude-based method. As the inverted impedance has not only eliminated the wavelet influence but also added the drilling information in the initial earth model, it is widely suggested to be better correlated with the reservoir quality than the seismic amplitude (Zhang et al, 2011a;Yang et al, 2007). We conduct the impedance inversion based on two different LFMs respectively constructed from the traditional and proposed methods.…”

“…The Ordovician carbonate reservoirs in this field are deeply buried (>5000m) and characterized by strong heterogeneity and some degree of anisotropy. These reservoir spaces are formed by a product of complex karstification related to unclear paleokarst drainage systems and subsequent complicated tectonic disruptions during burial (Zeng et al, 2011;Sun et al, 2012;Zhang et al, 2011a;Zhang et al, 2011b). To reasonably describe this strong heterogeneous reservoir and hence achieve accurate properties for prediction, we propose an amplitude-based modeling method by utilizing the heterogeneous information from seismic data to guide the geological model construction, based on the inverted pure P-wave data which have removed the AVO effects.…”

Frequency Domain Wave Equation Inversion and Its Application on the Heterogeneous Reservoir Model Data

“…The storage spaces for the carbonate reservoir in this area are mostly secondary dissolution caves and characterized by strong heterogeneity (Zhang et al 2008;Zeng et al 2011;Yang et al 2012). How to accurately image these dissolved caves plays a key role in exploiting the reservoir and reserve estimation (Zhang et al 2011;Tang et al 2012). Due to low signal to noise ratio, the accuracy of velocity model used in pre-stack migration is very important.…”

The Comparison between Full-Stack Data and Pure P-Wave Data on Deeply Buried Ordovician Paleokarst Reservoir Prediction

“…These anomalous amplitudes are associated with high-velocity limestone matrix and low-velocity reservoirs and are often regarded as the best indicator of good reservoirs. Zhang et al (2011a) suggested that a dissolution reservoir with a low velocity compared to the tight carbonate matrix can be recognized at the seismic scale if its dissolution thickness is larger than 35 m because the reservoir could then be imaged clearly in the post-stack seismic section. However, the seismic data quality is the fundamental factor which dominants the reservoir prediction.…”