Abstract

Multipay fields are often considered to be developed with a single well pattern, which is justified by economical efficiency reasons. Using smart well technologies is now on the highest peak of popularity. Although, such technologies allow intelligent monitoring and control to be performed, the most effective well regimes consideration is a challenging problem by itself. Because of system restrictions (casing diameter, wellhead pressure, infrastructure capabilities), regulating flow from/to one of the branches of such well can reflect on the overall system performance. Considering this, wells regimes should be worked out to give maximum economic efficiency. After the plan is worked out, control could be performed by choking layers with undesirable water/gas production (i.e controlling BHP).

Rosneft oil company operates Priobskoye field which has three productive layers (AC10, AC11, AC12) being developed. These layers are characterized with low permeability (1 to 20 mD) and different relative permeability characteristics which leads to non-uniform waterflooding and hence, difference in production watercut by layers. In order to perform monitoring and control procedures separately with each layer, it was considered to equip injection wells with special tools. A strategy of control for such wells is described in this paper. It is based on integrated study which includes NODAL analysis, watercut prediction and well tests. For injectivity curve (P,Q) characteristics (which is non-linear due to fractures development at high BHP), multi-rate tests are being performed. These tests allow obtaining non-linear injectivity characteristics to use it in NODAL analysis tool. Besides the method and case study, general recommendations are also given.

Introduction

Fields consisting of several layers (multipay fields) are often considered to be developed with a single well pattern for all of the layers, which is justified by economical efficiency. In such cases usage of smart well technologies is quite popular as they enable controlling performance of each productive layer independently. Moreover, smart wells or special inflow control devices are sometimes used in other applications such as steam injection control in heavy oil projects. Despite successful application cases constantly being published, very little or almost no attention have been paid to restrictions, capabilities and true economic value of such devices usage.

In contrast to regular wells, which have single bottomhole pressure, smart wells enable setting unique bottomhole pressure for each layer. Technically this can only be done by choking corresponding layer, which means that flowrate from each layer can only be reduced in comparison to the original value. Thus, technical efficiency of flow control (i.e. proper choking) can be achieved in two major cases:

  1. 2. Production from choked interval is undesirable. For example, in case if interval produces undesired gas or water;

  2. 3. Choking certain intervals can lead to increase of flow from/to other intervals.

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