Micro-Flux Control: The Next Generation in Drilling Process

Abstract

Drilling wells for oil/gas has been increasingly challenging with the companies moving towards difficult environments. The problems faced in these locations range from very narrow margin between the pore (or collapse) and fracture pressures, pore pressure uncertainty, to high pressure and high temperature wells. Wells drilled in these scenarios using the conventional drilling method often do not get to total depth (TD), and even so, drilling can be extremely risky, with several kick/loss situations. A new drilling method1 has been developed to overcome these problems, allowing a much safer condition, reducing the risks, and also permitting the wells to be drilled to TD much cheaper. Drilling is taken to the limit in a safe manner, extending each phase as much as possible, using the entire available mud weight window for that well. The method uses the new concept of micro-flux control, which is based on detecting a minimum loss or influx of fluids, and instantly adjusting the return flow and, consequently, the bottom-hole pressure to regain control of the well. The well is drilled closed at all times, and the return flow from the well is compared to the predicted and ideal one, allowing detecting the discrepancies in a very short time. This paper describes the basis of this new method and steps taken so far in the development. Field tests will be done very shortly, after the method has been tested in a simulated well condition. The use of this method allows wells to be drilled where today it has been impossible, extending today's technological limits way beyond the current boundary. Introduction Drilling wells for oil/gas is not a new activity, having started in the late 19th century. Despite being old, the drilling method has not evolved according to the development of new technology through the 20th century. It is essentially the same drilling method, using the hydrostatic pressure of the fluid inside the wellbore to control the pressures of the formations being drilled. There are several limitations of the traditional drilling method to drill wells in challenging environments. More severe operational restrictions, as well as environmental regulations, impose requirements that often make it uneconomical to drill wells in several locations around the world. Ultra-deepwater, high pressure and high temperature, and depleted reservoirs are just some. To overcome some of the problems caused by drilling traditionally in these environments, the industry developed some alternative techniques, such as underbalanced drilling (UBD), near balanced drilling (NBD), Low Head Drilling (LHD), and dual gradient drilling (DGD)2–15. All these alternatives were developed to solve specific problems and conditions caused by the traditional drilling method, such as loss circulation, formation damage, low rate of penetration, mainly caused by excessive overbalance pressure. Even though these alternatives are a step ahead from the conventional way of drilling wells, and bring significant improvement for the operation as a whole, they are far from being practical, economical, and being able to be used in a majority of the wells or even formation intervals. Therefore, they are still being used in a very restricted number of wells, in a niche market. On one side these alternatives can reduce the risk or make wells possible to be drilled, but, on the other side, they bring also severe side effects, as the equipments and techniques involved are more complex and require additional training and extra supervision, raising the risks of the drilling operation. The new drilling method described in this paper1 was developed combining the best of each available drilling alternative, including the conventional method, so that the disadvantages of each one can be reduced or eliminated. The main goal is to provide total flexibility to the driller to select which way the drilling operation should be conducted, with total safety and simplicity in terms of equipment and procedures. The paper describes initially the traditional drilling method, emphasizing the main points and disadvantages. Then, the paper briefly describes the most common drilling alternatives available and under development, to specifically address particular problems. The new drilling method is then described, followed by the advantages and benefits compared to the standard method and also compared to the various alternatives methods available.

Simulations Comparing Different Initial Responses to Kicks Taken During Managed Pressure Drilling

“…The Dynamic Annular Pressure Control (DAPC) system (Roes et al 2006), micro flux control system (Santos et al 2003), and recently developed continuous circulation system (Calderoni et al 2006) were found to be the technologies pertinent to CBHP method of MPD. However, no publications on well control methods for the CBHP method were found.…”

Optimizing and Automating Pressurized Mud Cap Drilling with the Micro-Flux Control Method

“…The MFC method has been described in previous publications [6][7][8] and only a brief decription is given here. MFC is an advanced, automated closed-loop system based on detecting either a fluid gain or fluid loss, and keeping the volumes of either event as small as possible -a microinflux or micro-outflux.…”

A Novel Dynamic Model for Predicting Pressure Wave Velocity in Four-Phase Fluid Flowing along the Drilling Annulus

“…Due to those efforts, research of the dynamic pressure wave velocity is of great significance to the detection of gas influx and effective control of the pressure at the bottom of well [3]. During the drilling operation of the so-called "microflux control, " an MPD technique developed by Santos et al [4], the return flow is monitored and adjusted to control fluid loss or gain. In the light of control principal, simulation studies were performed to determine the most appropriate initial response to kicks arising due to MPD specific complications caused by BHP fluctuations [5].…”