What are the key differences between a cased and open well cleanout?
Schlumberger: One key difference between the two is the level of potential risk. Open hole cleanouts are riskier than cased hole cleanouts due to the increased likelihood of fluid loss resulting in less efficient solids lifting capabilities. There is also a well integrity risk in open hole by the introduction of different chemicals or mechanical jetting tools required for an effective cleanout, resulting in a potential collapse of the open hole section resulting in stuck pipe. As a result of these risks, open hole cleanouts require extensive pre-job planning and measurements to ensure an effective and safe operation.
Baker Hughes: In an open-hole cleanout, the consideration is to minimize the damage to the formation and filter cake while effectively removing the debris. Mechanical tools that have direct contact with the hole ID, such as the scraper and brush, are typically not used in an open hole cleanout operation. The open hole cleanout is achieved mainly through chemical treatment and effective circulation. In cased hole cleanout, the mechanical tools, combined with chemicals, are the main methods to achieve the casing and hole cleanout. The tools are typically rotated at a relatively high speed to assist the cased hole cleanout, especially in deep and deviated well applications; while in an open hole cleanout, the rotation of the tool string needs to be avoided or controlled at a very low speed.
Halliburton: The main difference between a cased well cleanout and open well cleanout is additional risks in the second case. These risks are associated with additional fluid losses to the formation (risk of formation damage), wellbore sloughing or collapse, and risk that equipment could get stuck. So, for open wellbores, we need to use other technologies and programs for treatment. These approaches may be foam cleanouts or less aggressive cleanouts using additional chemicals to protect formations.
In uncased completions it could be difficult to place the treatment and could result in treatment loss to un-needed zones/formation. This can increase the treatment cost or reduce effectiveness. Uncased completions also reduce the choice of equipment that can be used for clean outs and may increase need for application equipment.
Is there a risk of formation damage by conducting a cleanout operation?
Schlumberger: There is a risk of formation damage during a cleanout operation particularly when the reservoir has sensitive clays, the lost fluid is unconditioned or has high solids content and non-degradable polymer content. The industry has sophisticated models that help us calculate differential pressures during cleanouts, but these models are based on manual inputs that are not always accurate. In order to ensure that a well is under balanced or at balance conditions during a cleanout operation to avoid formation damage risks, differential pressure at the nozzle needs to be monitored in real-time, which is possible with Schlumberger's ACTive technology. The ability to monitor and adjust key pumping parameters helps the engineer to act confidently and immediately while the coiled tubing and the tools are still in the well. With operating costs being driven down and especially scrutinized in today's environment, you need to make sure you get the most out of a well intervention.
Baker Hughes: There are always risks when operating in an open hole cleanout operation. However, by utilizing the right technologies and processes, the risk of formation damage is minimized. The fluid used to drill the open-hole reservoir section is designed to form a thin, removable filter cake that protects the formation from damage. When starting open-hole completion operations, it is typically recommended to displace the open-hole section with a clean fluid prior to pulling up into the casing to start the cleanout process. After the completion assembly is run, the filter cake that is protecting the formation is removed in a subsequent step so that it no longer impedes the production of oil or gas.
Halliburton: Yes is the simple answer (also see our response to Question 1). When selecting a chemical solution it is very important to consider the possible risk of formation damage. During cleanout operations there is a risk of getting fluid in the formation where it can react with the mineral composition of the formation resulting in reduced permeability. This issue has to be given special attention when recommending an acid treatment. Another risk, for instance, is the possibility of creating an emulsion in the wellbore area.
Can you outline a successful cleanout you have run in the region?
Schlumberger: In Western Siberia Schlumberger has performed successful proppant clean outs of multi-layered oil formations after AbrasiFRAC* Through Tubing operations on 5 zones. Apart from cleaning out wells completed in layered formations with potential cross flow between zones, an additional challenge is performing an effective cleanout in highly deviated wells with casing sizes of 146 mm OD. To overcome these challenges, the proper CT string design, cleanout procedure and fluid systems are designed with the help of our integrated cleanout software. Field crew experience and operational efficiency has led to many more successful cleanouts in similar conditions, enabling major operators to optimize recovery from their oil fields in Western Siberia through stimulation techniques made possible by advances in wellbore cleanout solutions offered by Schlumberger.
*A mark of Schlumberger
Baker Hughes: In the Russia Caspian region Baker Hughes has extensive experience in running Baker VACS Junk catcher inside Casing. In one of these job's for a customer in Belarus, we ran the Baker VACS tool in 6-5/8" casing for a MLT (Multilateral technology) Level 4 project and wherein the tool was run to clean out casing after whipstock retrieval in order to set the LEN (Lateral Entry Nipple) with anchor into the ML packer. We have done several such jobs for a customer in East Siberia. Also Baker Hughes have done several jobs with CT cleanout, using 1.69", 2.13" & 2.88" Motorhead assemblies and required accessories in Komi and Siberia.
Halliburton: Multi-Chem is a new business line of Halliburton and this is the first year of its operations in Russia; however, Multi-Chem is very well-known chemical supplier in the U.S. and Canada. Multi-Chem is involved in a few coiled tubing cleanout and gas well deliquification projects in Russia.
Mechanical methods are fundamental for efficient wellbore clearance. Vigor offers a comprehensive range of proven tools: casing scrapers for scale/wax, robust brushes for soft debris, and powerful magnets for metallic junk retrieval. Understanding diverse well challenges, we continuously refine these solutions. Vigor maintains deep expertise and a vast supplier base to provide the optimal mechanical tool for specific downhole conditions, ensuring thorough debris removal without relying on chemicals or jets. This commitment makes Vigor's mechanical tools the trusted choice for leading operators. Solve your debris challenges mechanically with Vigor. Consult our specialists today. For more information, you can write to our mailbox info@vigorpetroleum.com & mail@vigorpetroleum.com.
