Determination of Reservoir Parameters During Development of Well by Swabbing

Determination of reservoir hydrodynamic properties (permeability and skin-factor) is important for the calculation of the well productivity index (PI) and the assessment of near-wellbore formation damage. The calculation of the reservoir properties is based on the pressure transient analysis (PTA) and can be performed during the well development after drilling (after workover) or during the pressure welltest. This technique of the reservoir properties assessment during the well development has already become a common practice. The whole operations, the same as production logging survey (or as PL), easily fit in the production technology planning of well development and allow the quantification of reservoir hydrodynamic properties. There are some features for the marginal production wells.

For the development of the low-margin wells, since natural lift is getting impossible, this is a common to use swabbing in Russia oil fields. Another technique to supply the artificial lift is the gas-lift method while either the air or inert gas are being injected in the annular space of the well to ensure the fluid flow by gas lift supplying. Conventional liquid jet pumps are also used on the practice. During the swabbing operations it’s usually not possible to perform pressure buildup test (PBU), thus the technology of the liquid-level buildup (LBU) in the wellbore is implemented, and in this case the change of the wellbore pressure is caused by the continuing inflow of liquid from the reservoir to the open wellhead.

It is known that for the analysis of the downhole pressure data (buildup test), when there is an impact of post-flow, the simultaneous determination of the formation permeability and skin-factor is not reliable. The main interfering factor is a strong influence of the continuing fluid inflow impact from the reservoir on the borehole pressure after well just has been shut-in (wellbore storage effect – WBS).

This work discusses the practical examples of the implementing the new technologies related to e-line instrument called as MGDI (module for hydrodynamic investigations), which easily can be combined with well development by swabbing. The main approach of the technology is the overlapping of internal annuli of the production tubing by MGDI tool conveyed by the cable. It is supposed to reduce the time of survey and this operation is expected to provide the reliable determination of reservoir pressure, permeability and skin-factor.