Peculiarities of gas flow in reservoir in the presence of a skin zone
UDC: 622.279
DOI: -
Authors:
ALIYEV I.N.
1
1 Azerbaijan State Oil and Industry University, Baku, Azerbaijan
Keywords: permeability, contour and bottomhole pressure, dynamic viscosity, volumetric flow rate, density, temperature
Annotation:
Numerous studies have shown that in the process of drilling and developing low-permeable complex formations, engineers are forced to make great efforts and bear significant costs associated with technologies application at all stages of reserves involvement in gas fields development. The technology of wells completion and productive formations exposing is of particular practical importance. It should be noted that the physical-chemical properties of drilling muds and well killing fluids are also the object of study. For a deep assessment of various factors impact, the specific productivity coefficient of wells is often used in practice.
It should also be noted, that unlike oil wells, in gas wells the concept of the well bottom zone is deeper and more complex. The occurrence of a skin zone, water or natural gas separated from oil also creates additional resistance in the well bottom zone. This parameter partially reduces the permeability and porosity of the formation well bottom zone, thus ultimately reducing a gas well productivity.
To assess the negative impact of drilling mud and water in the gas formation production on the well bottom formation zone, the skin-zone and skin-factor parameters are taken into consideration. The degree and character of a formation opening are of special attention when developing gas fields as the skin-factor determines the filtration resistance that occurs in the well bottom zone. Due to gas wells imperfection there occur a complicated heterogeneous flow which is explained by essential deformations of the formation and flow.
It should be noted that the main reason for a skin factor occurrence is the filtration characteristics of the well bottom zone. Rather often parameters of this zone differ significantly from the corresponding properties of the formation. Partial or complete contamination of the zone adjacent to the well bottom section of a well causes deterioration of filtration characteristics and large losses of reservoir energy should be taken into consideration.
The author of the article proposes a method of the skin-factor calculation during gas wells operation. Based on the results of the study it is recommended to determine the value of the skin-effect factor, compare the well with the skin-effect with the well without it and propose methods of affecting the well bottom zone of a gas formation.
Taking into account the fact that skin-factor complete determination is very difficult, the specialists use approximate values. However, this method demonstrates positive effect in many cases.
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