This study concerns the mature Gyda reservoir, where some recent production wells have underperformed relative to equivalent initial wells. In particular, a sidetrack to an early successful well had very poor performance on initial startup. Subsequently, the geometry of both the original well and the sidetrack was simulated. In the original well, an attempted hydraulic fracture was assumed to have failed. This assumption was challenged in the model. The model has enabled evaluation of old wells and, more importantly, design of new wells in this mature-reservoir development.

Introduction

Gyda is a mature oil development in the Norwegian sector of the North Sea. The first production wells were drilled more than 20 years ago. Some recently drilled Gyda wells have not fulfilled production objectives. A numerical 3D model was proposed in order to investigate and understand the flow dynamics and the production potential from the Gyda A19 and A19A wells. This modeling process includes a detailed numerical 3D fluid-flow simulator based on computational fluid dynamics (CFD), which captures the reservoir, well, and completion geometry complexity.

The CFD simulations are used to determine potential explanations for the wells’ performance and lead to stimulation options and development of optimum drilling and completion for future wells. Because Well A-19 is very similar to Well A19A, some conclusions may be derived from the present study that could support the understanding of the productivity behavior of Well A19A.

To achieve the objective, one CFD model of both wells was constructed. Different completion options were provided, including the case of the hydraulically fractured well. Several sensitivity analyses were carried out in order to depict the well potential.