3.8.3. Selective and Spot water flooding.

To regulate the deposit development there are applied spot and selective water flooding, where injection and producing wells are situated not in accordance with the ordered development system, but in the separate areas of the formation. For this purpose the project backup wells are used.

Spot water flooding is currently used as additional measure to the basic system of flooding. It is carried out in the deposit zones where oil reserves are not recovered because of heterogeneous structure of formation, lenticular character of sand bodies bedding and other reasons. The position of injection and producing wells is determined so that to ensure full coverage of oil deposits impact. The number of water flooding spots is determined by the size of the oil-bearing area. It can be used in combination with edge water flooding system and especially with the circle water flooding to recover oil reserves that are not covered by the basic system. This system is very effective during the late stages of development.

Selective water flooding system is applied in the case when the deposits have high heterogeneity of formations. The peculiarity of this type of flooding is that at the beginning the wells are drilled according to the uniform square grid, without distinction between recovery and injection wells, and after some research and development cycle there are chosen the most efficient injection wells. Thanks to this method, the most intensive flooding system can be used with the fewer number of wells and more complete reservoir coverage by the flooding is achieved.

3.8.4. Barrier water flooding system.

A special type of water flooding – barrier water flooding is used during the advanced development of oil part of oil-and-gas deposit. Injection wells of barrier flooding cut off the gas part of deposit from the oil. It prevents the gas breakthrough from the bottomholes of the oil wells, displacement of gas-oil contact to the oil-bearing area. Barrier flooding reduces gas factor in times, in comparison to the development without stimulation. Gas wells are used to reduce the pressure in the gas cap (fig.3.13).

The wells of barrier flooding are situated on the inner gas pool outline.

Fig. 3.13. Barrier water flooding system.

1 – injection wells of edge water flooding system; 2 –injection wells of circle water flooding system; 3 – oil producing wells; 4 – injection wells of barrier water flooding system; 5 – gas producing wells; 6 – external oil pool outline; 7 – inner gas pool outline.

CHAPTER 4. FORMATION PHYSICAL MODELS AND DISPLACEMENT CHARACTERISTICS.

The model considers the created structure, reproducing or reflecting the researched object [7].

The formation model is the system of quantitative representations about its geological structure, taking into account lithological and pool-reservoir properties.

The development process model is a system of quantitative representations about oil and gas recovery from the interior.

The models are based on physical laws that define static and dynamic processes in the development process. The development models are described by the mathematical ratio of physical laws.

Nowadays to control and design the development process there are used geological and hydrodynamic models.