Performance of Multilateral Wells

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ABSTRACT

Field development has adopted a new alternative in the form of multilateral wells because this type of wells are capable of increasing the productivity per well and can also assist in reducing the field development capital. In some conditions, reservoirs are unable to support multilateral wells; therefore proper verification must be done to measure well performance prior to making decisions. Horizontal wells have an association with undulation to some extent. For this purpose, inflow performance models are taken into consideration. However, the current inflow performance models have failed to counter the undulation, and this has resulted in economic loss and also produced significant errors. In addition, few inflow models have the tendency of ignoring the pressure drop along the lateral, which definitely proves incorrect in extended lateral wells and extended production.

This study focuses on the development of inflow performance models for multilateral, undulating and horizontal wells. The inflow models can be separated into two main types; the line source model and the closed form model. The line source model works well with permeability and does not show any restrictions. The model is used for systems that are single phased and provides accurate results. In contrary, the closed form is used for the single as well as for two phase systems but for comparatively less vertical permeability formations. This model also provides results with reasonable accuracy. The well performance of unconventional well trajectories can be predicted and optimized as a result of this study.

TABLE OF CONTENTS

ABSTRACT2

INTRODUCTION4

Objectives6

MULTILATERAL WELL PERFORMANCE7

Introduction7

Closed Form Model of Two-Phase Multilateral Wells8

Model Assumptions8

Model Description9

Calculation Procedure10

Comparison of Single-Phase Model with Two-Phase Model12

Line Source Model16

Calculation Procedure16

Parametric Study17

Effects of Gas Oil Ratio18

Effect of Oil Gravity19

CONCLUSIONS21

Conclusions21

Recommendations22

INTRODUCTION

Oil and gas field development has introduced some new technologies and multilateral wells are one of them. These wells provide various benefits and their major benefit is the enhancing of per well productivity which subsequently reduces the number o f wells as well as the cost associated with the field development. However, these types of wells prove to be complex in both well structures and reservoirs. In addition, they also require higher drilling and completion costs; therefore proper verification must be done to measure well performance prior to making decisions. Performance models for wells can prove highly significant in various activities including; production optimization, development of field, well model and reservoir supervision. For these tasks, it is highly imperative to acquire a accurate and reliable inflow performance model.

There are two main methods used for the analyzing of well productivity which include; numerical simulation and analytical solution. The first method, i.e. the numerical method, demands a large data as input for describing the reservoir system and requires a lot of time. In order to gather the location and trajectory of the well, refined grids are usually required, especially for well structures that are complex. However, usually, numerical simulation models neglects the wellbore pressure drop. The dropping of wellbore pressure proves to be a serious factor for well performance, particularly for complex well ...