Enhanced dynamic interpretation from correlating well activity to frequently acquired 4D seismic signatures

Abstract

Quantitative 4D seismic interpretation can be successfully achieved by exploiting the causal link between the temporal variation in well activity and the 4D seismic signatures they induce. This is achieved by capturing in mathematical form the common interpretational practice of identifying the origin of dynamic signals in the 4D seismic volumes or maps on the basis of their association with a particular injector or producer. Thus, for example, a region of reservoir hardening (impedance increase) around a producer may be interpreted as a signal of pressure decrease. Similarly, an area of softening (impedance decrease) around an injector is interpreted as a signal of pressure increase when pressures are above bubble point. In the literature, a hardwired integration between the seismic and engineering domain has been obtained to some extent using methods such as seismic history matching, where the observed seismic and well production history data are simultaneously fit by predictions from a common simulation model. However, this approach is computationally expensive and suffers from nonuniquenesses, inaccuracies in the petroelastic model, and is ultimately only as accurate as the model itself. As an alternate approach, we reconcile here the well production history and time-lapse seismic data in the data domain without the need for a model. This approach involves the use of many frequently repeated seismic surveys shot over the same field, and mathematically correlates changes in the mapped seismic attributes directly to the fluid volumes injected and produced from the wells. Thus, well data normally used exclusively for history matching in the reservoir engineering domain can now also be directly integrated with the time-lapse seismic data.

Practical Applications of Time-lapse Seismic Data

“…In some of the earlier efforts to use 4D data as a history-match constraint, Huang et al (1997Huang et al ( , 1998 and apply a map-based, semiautomated method. The seismic misfit is defined by the normalized crosscorrelation of a 4D attribute, such as impedance change, with the depth-averaged model prediction of that attribute.…”

A method to update fault transmissibility multipliers in the flow simulation model directly from 4D seismic

“…Also, whilst 4D seismic signatures controlled predominantly by pressure or saturation changes are to be preferred for our technique, mixed controlling factors prove more challenging. A possible solution is offered by the multiple survey well2seis technique of Huang et al (2011).…”

“…In general terms, it is understood that the 4D seismic signature is sensitive to changes of water and gas saturation and also pore pressure resulting from the injector and producer activity. Indeed, when calibrated with well historical data it has been shown that 4D seismic signatures can be quantitatively related to the water saturation and pressure changes in the reservoir (MacBeth et al 2006) or simply well activity through fluid volumes alone (Huang et al 2011). Following this development, here it is believed that the overall spatial variability of 4D seismic amplitudes can assess the continuity of the reservoir changes in particular fields, and in turn this can be used as an aid in quantitatively interpreting discontinuities attributed specifically to the faults.…”

Enhancement of dynamic reservoir interpretation by correlating multiple 4D seismic monitors to well behavior

“…PRM such as life of field seismic and ocean bottom cable will therefore enable the generation of the most stable and reliable correlation properties. According to studies over several fields from the North Sea (Huang et al, 2010(Huang et al, , 2011Huang and MacBeth, 2012;Yin and MacBeth, 2014), a minimum of five repeated seismic surveys are required for the technique to work. To ensure the robustness of the correlation product and reduce ambiguities, a threshold value is required for the W2S attribute.…”