Recovering Tight Oil Geophysicists take the floor

April 21, 2014

structure of Bazhenov formations. The gathering of quality data and use of advanced data processing technology (azimuth seismic inversion, for instance) helps acquire valuable information that locates most favorable blocks for development and their geomechanical properties, as shown in figure.







OGE: Is microseismic investigation of use in the Bazhenov or Achimov? How is it best applied?

Tikhonov: Microseismic monitoring data provide valuable information on geomechanic  properties of developed reservoirs, which allows to optimize parameters of a multistage frac, the key instrument in producing tight reservoirs. However, as shown by the analysis of development of existing shale plays in the United States and Canada, the volume of microseismic monitoring of hydraulic fracturing doesn’t exceed 3 percent of the total number of operations, the reason being the high cost of survey. Microseimic monitoring is conducted by placing receiving sensors (seismic aerial) in one or several wells close to the frac wellbore. The placement of sensors on the surface is not justified, as a rule, because of the scarce energy of microevents of the frac. Valid examples of microseismic monitoring in West Siberia, which include not only the results of microevents positioning, but also the recordings of seismic signals, haven't been published yet in trade magazines. The greater part of tests that were conducted in West Siberia couldn’t reliably disclose and correlate on the basis of seismic recordings longitudinal and shear waves linked to a microevent. Evidently, the companies experienced in microseismic monitoring at intensively developed shale plays should be hired at a certain point to perform this task.

OGE: What other techniques are useful?

Tikhonov: As noted earlier, it’s useful to conduct high-density wide-azimuth seismic survey with individual sensors in an effort to obtain high resolution imaging and attributes that characterize interior structure and elastic properties of a tight reservoir. It is necessary to study the mineral structure of the rock as flooding during maintenance of reservoir pressure could cause changes in rock texture due to growth of volume of clay minerals and, accordingly, reduced permeability. It is useful to perform a set of logging tests to determine the total quantity of organic matter. In order to study the structure of the fractured-porous space, it is recommended to perform microscopic analysis and tomographic survey of core samples. Today, there are many ways of creating a 3D digital model of the porous space, which serves as the base for modeling and designing solutions to develop tight reservoirs that have been more difficult to produce due to natural fractures. It is necessary to develop and use the methods of scaling results of core samples and transpose them on a field as a whole.

If we focus on issues related to development of tight reservoirs, doubtless innovation is the frac design that takes into account a reservoir’s natural fractures. The majority of reservoirs have them and in this case the frac should be targeting to expand the existing fractures, not to create new ones. This