A Numerical Model Coupling Reservoir and Horizontal Well Flow Dynamics—Applications in Well Completions, and Production Logging

Abstract

A fully implicit, three-dimensional simulator with local grid refinement around the wellbore is developed to solve reservoir and horizontal well flow equations simultaneously, for single-phase liquid and gas cases. The model consists of conservation of mass and Darcy’s law in the reservoir, and mass and momentum conservation in the wellbore for isothermal conditions. Establishing the continuity of pressure and preserving mass balance at the sandface satisfy the coupling requirements. The proposed simulator is tested against and verified with the results obtained from a commercial code ECLIPSE-100™, and available public domain simulators and semi-analytical models. The proposed model can be used for multiple purposes such as well productivity prediction, transient analyses, well length optimization, completion design and optimization, and production logging interpretation. Different completion scenarios and reservoir anisotropy are simulated and their effects on the productivity of the horizontal wells are discussed. Completion cases include open-hole and partial completions. During the production logging of a horizontal well, the coil tubing reduces the wellbore cross sectional area and may cause substantial changes in the wellbore flow behavior. Depending on the well and coil tubing diameters, a significant difference between the actual production rates and the rates obtained from a production log can be observed.

Modeling of Coupled Reservoir and Multifractured Horizontal Well Flow Dynamics

“…However, predictions obtained with this simplified and idealistic uncoupled approach can lead to significant deviations from the actual behavior, especially in high permeability systems. This issue has already been addressed previously by the authors [14][15][16] ; however, due to the magnitude of the errors and complexity of multi-fractured systems, it deserves to be stressed over again. The correct representation demands a model that couples and solves simultaneously reservoir and wellbore flow dynamics, similar to the one that is described in this work.…”

“…For isothermal conditions, a comprehensive model coupling reservoir and horizontal well was presented by Vicente et al [14][15][16] for single-phase slightly compressible fluid and two-phase oil-gas flow. For a wellbore in the x-direction, flow behavior is described in terms of pressure and actual velocity using a mass balance equation and a momentum balance equation that accounts for inertial, friction, acceleration and gravitational components, as follows:…”

“…[14][15][16] The challenge increases significantly if the wellbore hydraulics is incorporated in the formulation but, at the same time, the solutions can deviate dramatically from the actual behavior if infinite conductivity approach is used to represent flow behavior in the horizontal well.…”

Equivalent Skin Factors for Nonuniformly Damaged Horizontal and Multilateral Wells

“…Several groups of researchers have investigated the impact of formation damage on horizontal well performance by using numerical models or commercial simulators. [21][22][23][24][25][26][27][28] In the numerical models, two different methods are used to quantify the skin factor; direct and indirect methods. In the direct method [21][22][23][24][25] , formation damage is generally mimicked by assigning a reduced permeability to the grid blocks surrounding the wellbore.…”

“…[21][22][23][24][25][26][27][28] Most recently, a numerical model to characterize the formation damage due to use of water-based-mud and natural cleanup during production has been proposed. [26][27][28] The numerical model presented by Ding and co-workers [26][27][28] is capable of predicting the horizontal well performance under the influence of unevenly distributed formation damage.…”