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Use of Dynamic Simulations To Prepare a Dual-Gradient-System Field Trial

This paper reports results of a well-control study for a program to develop a dual-gradient-drilling (DGD) system known as controlled mud pressure (CMP). Conventional well control may not be possible when using dual-gradient systems, because a chokeline full of heavy mud may fracture the formation, making well control a major obstacle to implementing DGD offshore. The project developed several well-control methods, and one was selected for field testing after a risk-assessment process with the operator.

Introduction

While DGD solves many deepwater drilling problems relating to wellbore pressure (please see the complete paper for a discussion of the principles and applications of DGD), it may require new procedures for well control. This depends on water depth and how much the mud weight is increased. New well-control procedures will be necessary because the heavier drilling fluid in the well will exceed the formation’s fracture-pressure gradient if allowed to fill the chokeline and create a full column back to the surface. This potentially dangerous condition can result in formation breakdown and potential loss of well control.

It is also possible to apply DGD without extending casing depth. In this case, DGD will provide increased margins, and in some cases conventional well-control procedures may be applied.

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper OTC 25360, “Dynamic Simulations of New Well-Control Procedures Used To Prepare a Dual-Gradient-System Field Trial,” by J.H. Cohen and R. Stave, Enhanced Drilling, and E. Hauge, J.M. Godhavn, and D.O. Molde, Statoil, prepared for the 2014 Offshore Technology Conference, Houston, 5–8 May. The paper has not been peer reviewed. Copyright 2014 Offshore Technology Conference. Reproduced by permission.
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Use of Dynamic Simulations To Prepare a Dual-Gradient-System Field Trial

01 September 2014

Volume: 66 | Issue: 9

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