Worldwide, the research groups have been dealing with several innovative drilling technologies. Their common aim is to significantly decrease the overall price of the drilling process, particularly to keep the high constant speed, energy efficiency and shorter drilling time. There are above twenty innovative non-contact technologies at different maturity such as: laser, water jet, plasmatorch, ultrasonic, microwave, and several others. However few of them reached Proof-of-the-Concept in laboratory and are currently developed in outside testing sites. This paper presents one of such activities -development of technology based on electrical plasma for hard rock drilling. During its development, another application was identified -milling of steel casing and cement for well Plug&Abandonment operations. Both of these applications are developed by the team of engineers led by the authors.The electrical plasma-based tool changes completely from its inception the paradigm of the drilling as well as casing milling. The most important advance in comparison to conventional plasmatorch technology is that the electrical arc with temperatures of tens of thousands of degrees Kelvin heats directly the surface, especially the radiation component, with minimalized heating of intermediate gas (the intermediate gas flow in conventional plasmatorches reduces the efficiency of heat transfer into the rock). Moreover, the arc creates area-wide, relatively homogeneous heat flow from spiral arc on the whole surface for high-intensity disintegration process. Compared to conventional plasmatorch technology, electrical plasma-based technology allows the use of electrohydraulic phenomenon, generating shock waves for the destruction and transport of disintegrated material. System also allows obtaining electrical and/or optical characteristics of the arc in the interaction with the rock to derive indirect sensory information (e.g. online spectroscopy for logging while drilling.). This paper includes the nature of challenges in both application areas -hard rock drilling and casing milling, the description of the developed solutions, the results obtained until now, possibilities of some spin-off technologies using the same core technology concluded by expected impacts. The technology has been tested on various rock types including sandstone, limestone, halite, granite and quartzite. Currently, the demonstration prototype is being tested for drilling of testing borehole in the quarry.
Plug and Abandonment (P&A) is the largest category in Decommissioning expenditures, representing 40-44 percent of the total investment that basically comes as mandatory cost with no expected return. If the well operator gets P&A inadequate, results may include water flows, gas or oil seeps from the seabed, or underground cross flow between formations with huge impact on environment and marine life. The objective of this paper is plasma-based technology for enhanced casing section milling addressing the P&A challenges.According to some oilfield service providers, two main P&A challenges are as follows: Time and expense of casing milling -for example, Norwegian regulations call for cementing two 50-meter sections of casing above and below each hydrocarbon-bearing zone. Each section may take more than 10 days to mill and may generate four tons of swarf. The second challenge is swarf damaging blow out preventer (BOP) -Milling generates swarf, which then must be removed before cementing. However, swarf removal can damage the BOP. To avoid well integrity issues, BOP has to be dismantled, inspected and repaired at considerable expense.The presented paper is focused on technology eliminating the P&A challenges. The core of the technology is based on plasma generator producing high temperature water steam plasma for rapid steel structural degradation. This approach brings a radical abandonment of the classic rotary approaches with connected tubes in long strings and generation of swarf which need to be removed. Besides elimination of aforementioned challenges, the technology advantages include also rigless operation since the system is designed for coiled tubing solution. This feature brings additional cost savings using Light Weight Intervention Vessel (LWIV). Moreover, fully automated coiled tubing goes hand in hand with enhanced safety of the operational staff.Impact and potential of the technology is to change, simplify the process of P&A and therefore significantly cut the time of whole P&A. The technology is currently under development with expected commercialization within three-year period.
The paper is focused on emerging plasma-based milling technology enabling wider use of Light Intervention while restoring Well Integrity. The tool should be able to RIH through tubing minimizing footprint of the equipment using coiled tubing system. The presented milling technology uses electrical plasma for material disintegration. A significant advantage is based on the size of disintegrated material when compared to conventional milling producing massive swarf / debris. Analysis of cuttings produced during casing / tubing milling with plasma-based tool shows that their size distribution is based on the major fraction in the range of 1-5 mm. This feature reduces possibilities of intervention failures related to swarf / debris in the well in order to maintain Well Integrity. The technology is currently under development with expected field testing in 2016. Currently, the technology´s application is focused on Plug & Abandonment (P&A) service while being developed within Joint Industry Project (JIP) with O&G operators and oilfield service provider. Parallel to JIP, the team is capable to customize the technology and the tool itself for applications like slot recovery, side-tracking and pipe recovery. The unique features of the plasma-based technology can be beneficial for several Well Intervention applications in the Middle East region.
The paper presents progress made in research and development (R&D) of emerging plasma-based technology for well intervention applications. The technology potential for various upstream applications has been presented at some other SPE conferences (March and September 2015 and January 2016). Current development phase, which is intended for well plug and abandonment (P&A) operations, allows planning applications relevant to modern well intervention needs such as slot recovery, re-entry, lateral drilling and several others. The experimental basis uses a project plan, which is adequate for development tasks and is periodically updated based on the achieved results. This paper presents results of the latest experiments which focused on the evaluation of cement removal ability and quantification of plasma radial reach. The paper includes several sections. The first section is Introduction, which briefly summarizes the background of the technology as well as introduces the scope of the experiments. The second section Methods and Procedures explains experimental set-ups, defines samples and procedures used for analysis. The third section Results and Observation describes in detail the main results obtained during extensive testing of the radial reach as well as the results obtained during experiments with three different types of water- and oil- based mud samples. Special attention is given to the result of the plasma impact on casing in case of eccentric position of tubing. The last section summarizes obtained results and presents the possible benefits of plasma-based technique on well intervention applications. Currently, the research team performs development of infrastructure and bottom-hole assembly (BHA) for tubing milling for onshore and offshore field trials. Moreover, high-pressure (HP) testing well for BHA tubing milling operation tests in high pressure of water/brine environment is also under development. The testing environment will serve for the proof of the system and should confirm the ability of testing in field conditions.
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