Seismic reservoir characterization in resource shale plays: “Sweet spot” discrimination and optimization of horizontal well placement

Abstract

Surface seismic data has proven to be an invaluable asset for organizations producing hydrocarbons from unconventional resource plays. Initially, one of the primary benefits of surface seismic was the ability to locate and avoid drilling into zones with faults, fractures and karsting which adversely affected the ability to complete the well successfully. More recent advances in pre-stack seismic data analysis yield attributes that appear to be correlated to formation lithology, rock strength and stress fields. Knowledge and proper utilization of these attributes may prove valuable in the optimization of drilling and completion activities. In this article we show an integrated seismic approach based on pre-stack azimuthal seismic data analysis and well log information to identify "sweet spots", estimate geomechanical properties and in-situ principal stresses.

Amplitude variation with incident angle and azimuth inversion for Young's impedance, Poisson's ratio and fracture weaknesses in shale gas reservoirs

“…; Harris, Miskimins and Mnich ; Sena et al . ; Sharma and Chopra ). Sharma and Chopra () determine the lithology and brittleness of rocks with a new attribute, which is the product of Young's modulus and density.…”

Prestack amplitude versus angle inversion for Young's modulus and Poisson's ratio based on the exact Zoeppritz equations

“…Seismic rock physics studies have shown that Young's modulus, Poisson's ratio, and density are related to quantitative reservoir properties such as porosity, rock strength, mineral, lithology, and total organic carbon content (Harris, Miskimins and Mnich ; Sena et al . ). Conventionally, Young's modulus and Poisson's ratio were computed indirectly from density and P‐ and S‐wave velocities or estimated based on the approximate Zoeppritz equations' inversion (Kurt ; Sena et al .…”

Pre-stack basis pursuit seismic inversion for brittleness of shale

“…The study of shale brittleness is very important for shale gas exploration and development. An empirical brittleness cut-off is defined based on Young's modulus and Poisson's ratio (Grieser and Bray 2007;Rickman et al 2008) as they control the relationship between stress and strain given by Hooke's Law (Sena et al 2011). A high-value anomaly of Young's modulus and a low-value anomaly of Poisson's ratio can be used to evaluate the rock brittleness and to infer ''sweet spots'' of shale gas reservoirs (Harris et al 2011;Zong et al 2013).…”

“…The ultimate goal of pre-stack inversion is to obtain the elastic information that can be used for evaluating hydrocarbon potential and the brittleness of the reservoir and to infer ideal drilling locations of ''sweet spots'' (Sena et al 2011). Different linear approximations (Aki and Richards 1980;Gray et al 1999;Russell et al 2011) of the Zoeppritz equation introduced by Zoeppritz (1919) help us to directly estimate the elastic parameters (e.g., P-wave velocity, S-wave velocity, Lamé parameters, bulk modulus, density) in which we are interested.…”