ABSTRACT

The horizontal section's maximum allowable length during tripping or running casing in the horizontal extended-reach well (HERW) is often much shorter than that of drilling operations, this results in a limited well depth for tripping or running casing operation. In this paper, a model for predicting the horizontal section's maximum allowable length during tripping or running casing in the HERW is presented. Mean during the factors affecting the horizontal section's maximum allowable length are also investigated. The results show that with the increase of tripping or casing running speed, the horizontal section's maximum allowable length first appears to decline sharply, and then tends to be flat. Given the safe mud weight window, the horizontal section's maximum allowable length during tripping or running casing is far shorter than that of drilling operations, and the casing running operation is the main limiting factor for the horizontal wellbore extension of the HERW. This work provides a practical tool for enhancing the design of the HERW.

INTRODUCTION

The development mode of the horizontal extended-reach well (HERW) and cluster extended-reach wells has significant effects. E.g. the efficient development of marginal oilfields, the effective resolution of conflicts in the use of the sea (ecological protection and shipping), the increase of platform radiation areas, and the reduction of oil and gas development costs (Chen, Gao, 2018a; Chen, et al, 2018b). However, when the extended-reach well exceeds the limit extension length, problems such as lost drilling fluid circulation, hole collapse and well control will become uncontrollable, and drilling operations will have to be stopped, which severely restricts the application of extended-reach well technology. Therefore, it is necessary to find the key factors that restrict the extension ability of extended reach wells, and form a method for predicting the extension limit of extended reach wells, which provides a strong technical support for the efficient oilfield development. This article will start with the open hole extension limit model (Li Xin, Gao, 2019) for the extended-reach well. It analyzes the change law and key parameters of the open-hole extended-reach limit of the HERW during casing running, tripping and drilling operations through an example. This article is intended to provide a reference for engineering practice.

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