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.
TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractUnderbalanced Drilling (UBD) can be compared today with the horizontal drilling technology 15 years ago. Most probably, the majority of the wells will be drilled underbalanced in the near future. While onshore and offshore operations from fixed platforms have been conducted, UBD from floating units is still a challenge. With the majority of its hydrocarbon reserves located in deepwater, Petrobras decided to start a project to develop technology to drill wells with light-weight drilling fluid from a floating platform. This technology is seen today as the first step to reach UBD from a floating vessel, including deepwater locations. The present paper describes the steps taken so far to develop all the new equipment required and the HazOp meetings to discuss and approve the technical details and procedures. The paper also discusses the difficulties encountered during the negotiations with a rig contractor, to allow and fully understand the operation on board of one of its platforms. The paper finally discusses the best options from the lessons learned so far to have rigs ready to use this technology in the near future.
Drilling wells for oil/gas in ultra-deepwater has been increasingly challenging. The major problem faced in these locations is the very narrow margin between the pore (or collapse) and fracture pressures, which leads to numerous casing strings needed and, in many cases, the wells end up uneconomical. Wells drilled in these scenarios using the conventional drilling method are extremely risky, and in order to overcome these difficulties several initiatives are under way to develop a dual-gradient method, which are extremely expensive.A new drilling method has been developed to tackle these problems, allowing a much safer operation, reducing the risks, and also permitting the wells to be drilled to TD (Total Depth) 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. This new method uses much simpler equipment than the mud lift ones, with very quick field implementation.Previous works 1,2 presented this method in detail; this paper will focus specifically on the method's application for deepwater 3 . The method brings clear benefits to environments with normal to slightly above normal pore pressure. However, in high pore pressure scenarios, it can also bring significant improvement in safety and minimizing downtime compared to the traditional way of drilling wells.
This paper was prepared for presentation at the 1999 SPE/IADC Drilling Conference held in Amsterdam, Holland, 9-11 March 1999.
Numerous developments in automation have made the modern mobile offshore drilling unit a marvel of engineering achievement and a model of efficiency. Yet, even with the surge in advancements, kick detection, which can be comparatively elementary for a fixed drilling unit, has proven significantly more difficult to master on a vessel which subject to wave motion and currents. A lack of consensus on universal standards and regulations have left kick detection largely ignored. But further, the lack of innovation has been coupled with drilling in greater water depths which are subject to the use of longer risers with greater volume and weight. Thus, in addition to the complications of dynamic environments are the material requirements to properly intervene during an influx event. Operators and shipyards have kept pace with these material issues by designing larger, smarter vessels with greater capacities and better controls systems to cope with the complexities of drilling in deepwater environments. Despite the best efforts and ballooning costs, influx events continue to occur because an operating envelope and a universal philosophy for deepwater kick detection have yet to be established.With the primary driver for deepwater and ultra-deepwater drilling being to access the most productive formations possible, a recipe is formed such that a slight variation between formation pressure and fluid pressure has the potential to draw a significant hydrocarbon volume into the well bore. When well control procedures are initiated, a series of checks take place which, though proven and reliable for detecting kicks, consume valuable response time and potentially aggravate the initial problem. After an influx has been confirmed, remedial work often takes days and sometimes weeks to recondition the well for drilling. Whether in terms of personnel, equipment, facility, environment, or finance, the risk presented to the drilling operation by influx and loss events is substantial. Therefore, an advanced approach should be adopted which views kick/loss detection as a safety critical measurement and incorporates a modern, control system based design philosophy with established methods to overcome shortcomings. This paper will describe experiences, challenges, and approaches to solving the problems related to creating an advanced early kick detection system suitable for floating mobile offshore drilling units. Necessary components, operational considerations, and design limitations will be discussed. Additionally, a discussion will offered on the current state of regulatory requirements related to kick detection and considerations for future standards.
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