Optimum Well Patterns and Well Paths Selection in Formation AV11-2 (Ryabchik) During Ust-Vakhskaya Area of Samotlor Field Development
Authors: Krasnevsky Yu. S. , Gorobets E. A. , Kundin A. S. , Podrezenko Yu.V. 
Published: October 2008

Abstract

Introduction
Reasonable well placement in the formation is one of the strategic objectives of efficient field development. Optimum well patterns and paths of well placement have been assessed to optimize oil reserves recovery from formation AV11-2 with applying a digital filtration model. A 3D sector simulation model of AV11-2 formation, Samotlor Field, provides for full description of the reservoir both lateral and vertical heterogeneity. This sector model has been used as a basis for development and further analysis of seven-spot patterns options with wells being of various configurations and having various performance.

3D reservoir simulation model
The reservoir simulation sector model was used to model a seven-spot pattern component. The model was developed on the basis of acting reservoir simulation model of AV11-2 formation, Ust-Vakhskaya area (Fig. 1) Reservoir properties of the model are specific to AV11-2 (Ryabchik) formation. X number of cells – 130; y – 130; Z – 23. The pattern horizontal size is 20m × 20m. Average thickness of hydrodynamic layers of oil-saturated portion of the reservoir amounts to 1.5 m.
The permeability varies from 1 to 30 mD within the model. Horizontal to vertical permeability ratio is 0.001. The designed well spacing is 600 m. The forecast well computations were executed upon fluid control specified (with regard to capability pre-design) for producers and injectivity specified for injectors in case of 100% compensation. Besides, the bottom-hole pressure has been specified: minimum – 50 atm.–for producers and maximum – 270 atm. - for injectors.

Review of forecast options
Option 1 is a part of a traditional seven-spot development pattern. All the wells are vertical fractured wells. The skin-factor specified both for injectors and producers is 4 (Fig. 2). Option 2 involves 3 horizontal wells with U-shaped paths of a horizontal well bore (Fig. 3) instead of six vertical producers. Option 3 has been developed on the basis of Option 2 with the path of horizontal producers changed to wave-like (sinusoidal) (Fig. 3). Option 4 has been developed on the basis of Option 3 where the horizontal producers were fractured (S=−3) (Fig. 3). Option 5 has been developed on the basis of Option 2 where two dual horizontal wells were drilled instead of three horizontal producers. (Fig. 4).
Option 6 has been developed on the basis of Option 4 where horizontal producers were fractured with the state-of-the-art technology applied (surgifrac) (Fig. 3). Option 7 has been developed on the basis of Option 1 where all the producers were fractured with AquaCon technology applied (Fig. 2). Option 8 has been developed on the basis of Option 4 with the vertical injector in the center being replaced with a fractured horizontal one (Fig. 5). Option 9 has been developed on the basis of Option 4 with each horizontal well being replaced with six vertical ones that have been perforated and the perforation interval is 6 meters, which is the depth of sinusoidal horizontal well hole making corridor (Fig. 6).