Technology Roundtable: Lost Circulation
1. In which regions of Russia are lost circulation issues consistently found?
Halliburton: In the current economic conditions, many oil companies focus on the development of mature fields. As a rule, such fields have well-developed infrastructure, and their investments have long ago paid off . However, the other side of the coin is that construction of new wells becomes more sophisticated. Low reservoir pressures, high water cut, more frequent fracs, considerable fluid production rates – all of these present extremely high risks for well drilling. One of the major well construction risks is lost circulation.
Lost circulation entails considerable costs and creates serious problems while drilling worldwide, and in the future this kind of a trouble would only escalate. In Russia, lost circulation is a well known issue for the Volga-Urals area (areas along Volga River, Orenburg area, Bashkortostan). In the areas of Eastern Siberia, Republic of Komi and North West Siberia this issue is less severe.
The key reasons for this issue lies in lithology and anthropological factors. Lithology and lithogenesis factors are the following: loose rocks (highly permeable sands, gravel, shelly rocks and reefal deposits), natural fractures (interlayers of sandstones and shale rocks, intervals under tectonic strain), caverns (cavities, pockets and faults). Anthropological factors include: depleted zones (low-pressure sandstones), induced fractures (mechanical impact in the process of well drilling or completion).
National Oilwell Varco: Lost circulation issues are mainly found in the Volgo-Ural (Orenburg area, Bashkortostan) as well as Western Siberia. We observe an increased demand in the loss circulation solutions in Komi Republic and Eastern Siberia too.
Weatherford: Lost circulation is one of the most common issues in drilling which significantly complicates the process. Fractured, cavernous rocks and highly permeable rocks may potentially be lost circulation zones; therefore this presents a pressing problem for most petroleum provinces in Russia – from the Caspian region to the Timan-Pechora province, from the Volga Region to Sakhalin. Lost circulation may be caused by process reasons or geological structure of rocks. It is commonly known that geological and lithological properties of rocks in various regions of our country may differ greatly, as well as the drilling technologies used; accordingly, the nature and reasons for lost circulation in various regions would be different. Well drilling in fractured and cavernous carbonate rocks, e.g. in the Urals, the Volga region or East Siberia is most challenging. In the southern regions of Russia lost circulation is often linked to reservoir permeability and drainage areas, especially if heavier muds are used.
Targin Drilling: In Central Russia. This includes Orenburg, Samara regions, Republic of Bashkortostan and Republic of Tatarstan. The causes of lost circulation are: late stage of field development, high-permeability formations, сavernous formations, fractures (Serpukhovian Stage, Myachkovskian Stage).
Other regions are YNAO and KhMAO in Western Siberia. The causes are the same; late stage of field development, high permeability, ALRP (Senoman Stage).
2. What are the most common problems relating to lost circulation?
Halliburton: Considering the a.m. reasons, the lost circulation problem is the key problem worldwide, and it is associated with a lot of evident and hidden risks for the customer.
One lost circulation impact is the loss of drilling fluid, which is often costly by itself. It costs us increased rig time and additional materials to replenish the lost volumes. We should not forget about the effects of lost circulation which seem insignificant at a glance. First of all, there are risks of additional chemical handling for people, and the environmental hazard of blowouts in case of a drastic drop of the drilling fluid in the well. In the worst cases, the above factors may lead to loss of the well, loss of life, drastic environmental damage and huge financial costs of response operations. Halliburton focuses on evaluating and predicting such risks even at the drilling planning stage. Primarily, we evaluate the risks to human life and health and risks of environmental impact. At this stage, the key driver is the expertise of our engineers, innovative specialist software (e.g. Halliburton offers DFG®, WellSET®, WellSight EXPRESS®, CFG®, DFG RT®, WSAnalyzer®), advanced materials and compositions for lost circulation control. Our success is largely supported by global experience in the application of our technologies with a huge database accessible by each company engineer involved in the well planning and construction process.
National Oilwell Varco: Partial or total circulation loss will entail an increase in well construction time, in particular, due to the non-productive time spent on curing it. Among the most common problems related to lost circulation are potential kic, differential or mechanical sticking, even potential loss of BHA.
Weatherford: Lost circulation accompanied by reduction in hydrostatic pressure creates favorable conditions for subsequent gas, oil and water shows, and may also lead to caving, or wellbore walls collapsing, which damages the general integrity of the wellbore. It may also lead to differential and mechanical sticking, equipment loss in hole, incidents and significant time and cost consumption to remedy the situation. Moreover, lost circulation may negatively impact the original reservoir properties of the productive intervals and, consequently, significantly reduce the flowrate.
Targin Drilling:
• Wellbore instability (loss of hydrostatic pressure on wellbore wall, sloughing).
• Gas-oil-water flow (loss of hydrostatic pressure on formations, flow). The shut-in pressure in the top hole bleeds down to the wellbore causing formation sloughing in the weakest spots which results in both flow and loss of well control. Preliminary studies, proper well engineering and proper drilling practice may mitigate the sticking risk and aggravation.
• Differential sticking caused by liquid head and reservoir pressure difference.
• Cost and time over-runs (additional trips, mud preparation).
• Tight wellbore due to thicker filter cake in the lost circulation zone and filtration.
• Poor well casing.
3. How can the well design plan help mitigate and prevent lost circulation?
Halliburton: The design stage is one of the most important early stages of well construction. Any well can and should be designed to meet the risks which may lead to troublesome situations. Close cooperation with the customer, experience, technologies – everything contributes to mitigation of lost circulation risks. Interval inclinometry, type of drilling fluid and mud rheology are all known to greatly contribute to lost circulation. The following scenario can be seen as an example: The customer provides data on the future well and equipment to be employed in drilling. Our experts simulate the hydraulic drilling conditions in the well. At certain conditions (e.g. small borehole diameter and large diameter of used drill pipes), the drilling fluid pressure in the well will cause hydraulic fractures in the poor formation, leading to lost circulation. In this situation, we recommend using the lesser diameter pipes (where possible), or using special drilling fluid additives, considerably mitigating the lost circulation risks. Our background proves the high level of correlation between theory and practice in this context.
National Oilwell Varco: Partial or total circulation loss will entail an increase in well construction time, in particular, due to the non-productive time spent on curing it. Among the most common problems related to lost circulation are potential kic, differential or mechanical sticking, even potential loss of BHA.
Weatherford: Pre-drilling modeling and risk analysis have now become an important phase of well construction, as they help minimize expenditure and reduce NPT. To prevent possible extra costs, well objectives and challenges should be explored already in the design stage of well construction. Then an optimized well plan should be engineered with the most suitable well-construction technology chosen, based not only on the project budget but on well and field data, etc. Such a balanced approach allows to minimize risk, deliver cost assurance and ultimately exploit ever more challenging reservoirs.
Targin Drilling:
• Isolation of zones with incompatible drilling conditions.
• Optimum drilling practice, optimization of hydraulic program to achieve proper cleaning and reduce ECD, especially in sensitive zones.
• Optimum mud composition depending on geological conditions.
• Close analysis of problems encountered in earlier drilled wells allows incorporating preventive measures in the design phase.
4. What are the key considerations when drilling through known vugular or highly fractured formations?
Halliburton: Unfortunately, there is no unique antidote to mitigate or prevent lost circulation while drilling through vugular or highly fractured formations. However, the means of minimizing the severity of the issue in such formations is well known – proper planning which includes best drilling practices, practices to prevent or combat losses, sufficient stock of contingency LCM of the right type in the right amount, optimized fluid rheology, pump rates etc.
Halliburton uses the software which has repeatedly proven its efficiency in this respect. In particular, the WellSET® module of DFG® software enables predicting the type and geometry of fractures (provided sufficient geological data are received from the Customer) and selecting the most efficient combination of sealants and drilling fluid additives out of those available in the given area of operations. DFG® allows us to select the most optimal drilling fluid system for given conditions. For example, it is possible to use the foam-based system QUIK-FOAM®.
National Oilwell Varco:
• Using LCM additives to mud before the L/C interval entering.
• Tripping speed control for swab/surge effect reduction.
• Logging while drilling of the pore pressure/ECD.
• Adequate hole cleaning.
• Monitoring mud weight as per program.
Weatherford: Profitability of well construction is ensured by such factors as increased rate of penetration, elimination of lost circulation and sticking, reduction of time for wiper trips and circulation, etc. However, one of the key objectives of efficient drilling is to expose the producing formation and ensure high permeability in the wellbore area even while developing assets in cavernous and fractured formations, which can become catastrophic mud loss zones. A well founded and cost effective lost circulation control method should be best selected based on geomechanical modeling. Its application in drilling allows analyzing the planned well profile for the feasibility of drilling and giving recommendations for drilling optimization and well design adjustments with account for anomalous zones (high/low pressure zones) and estimated safe drilling window.
Targin Drilling:
1) Mud type and weight.
Increased mud weight during loss of circulation shows that the latter is caused by hydrostatic pressure increase. Such lost circulation may go away by itself (filtration). Otherwise, when loss of circulation goes through induced cracks, the remedial measures should consider the lost circulation intensity.
2) Drilling practice (monitoring circulating mud rate, smooth startup).
Quick startup or shutdown of pumps may also cause pressure drops. The too quick startup of pumps induces pressure that may lead to loss of circulation, particularly during measures aiming to break circulation in annular space following the tool run. Swabbing creates pressure that breaks down the mud structure. Moving the pipe while breaking circulation facilitates gel break-down and significantly reduces impulse pressure. On the other hand, swabbing creates pressure that accelerates mud circulation and allows reaching normal circulation rate. The impulse pressure may be reduced by maintaining the gel structure on low level and gradually increasing the pumping rate. Another way to reduce such pressure is to run the tool with resuming the circulation by intervals.
3) Penetration rate (limiting the rate to improve colmatage in zones).
Changes in the drilling rate may indicate changes in the reservoir and therefore affecte formation integrity.
4) BHA (utilizing rotary BHA to reduce ECD and in treatments by LCM, reduce whipping).
The BHA neutral point should be maintained by using the required number of HWDP.
5) The mud rheology (increasing gel shear stress to form non-flowing layer in the hole zone).
5. When deciding how to mitigate an unpredicted lost circulation zone during drilling operations, what are the correct decisions and actions to remedy the situation as quickly and as cost effectively as possible?
Halliburton: There is no room for guessing while drilling the interval or when this scenario has already taken place. A proper decision tree for each particular scenario must be in place before the well is spudded. It is also critical to provide the drilling site with diverse (multimodal) materials with different functions. Halliburton uses a lot of various additives in its operations. These are conventional sealants and still exotic materials such as: micaceous carbonate – BARAFLAKE® M, swelling polymer with 400-fold expanding particles – DIAMOND SEAL®, spongeous materials such as BaraLock®-666 with various particle sizes.
Notably, the LCM approach may not help. This being the case, an alternative approach to well drilling may be required using emulsion drilling (underbalance drilling), foam drilling, etc.
National Oilwell Varco:
• Running circulating subs that help place the LCM saving an unplanned trip to the operator.
• Monitor ECD to prevent loss of circulation, controlled ROP (if needed).
• Lightening mud weight if it is possible. Review casing program.
Weatherford: Regrettably, there is no panacea for lost circulation, but anyway, an operator company and a drilling contractor would start from the simplest solution. In general, the best and most efficient means of lost circulation control is prevention. The existing methods of prevention and elimination of complications during drilling at various lost circulation rates or in case of complete loss of circulation include the following: lowering of hydrostatic and hydrodynamic pressure in a well (mud cap drilling, drilling with air or foam drilling), lost circulation zone plugging (using special cement mixtures and pastes), or plastering effect (while drilling with casing), using mechanical barriers (single use or drillable packers, or expandable patches).
Targin Drilling:
1) Change the mud type and weight;
2) Add and inject LCM;
3) Change rheology properties;
4) Adjust drilling technique respectively to drilling pump, drilling rate and BHA.
6. What products/services do you supply to overcome lost circulation problems?
Halliburton: Halliburton provides all known types of LCM materials, sealants and sealing technologies. As mentioned above, these are both conventional widely known materials, e.g. sorted crushed marble, and exotic and unique technologies. Amongst them are the most advanced developments in the field of multimodal materials combining all structural types of sealants (fiber, spongeous materials, swelling polymer, elastic particles, micaceous materials). Our experience shows that such materials are easily delivered and stored, they can be quickly added and prepared (which saves a lot of time) and help reduce the number of sealant pills. These materials (BDFTM -657, BARABLEND®-665, HYDRO-PLUG®) have been developed by Halliburton on the basis of accumulated experience as the most efficient combinations of various components.
National Oilwell Varco: MOCS (multi-opening circulating sub). Current sizes are 8”, 6 ½” and 4 ¾”. 4 1/8” is to be designed.
NOV Named Finalist for 2013 World Oil Awards: National Oilwell Varco has been named a finalist in three categories for the 12th annual World Oil Awards. The World Oil Awards serves as a yearly opportunity to spotlight important innovations and achievements in the upstream oil and gas industry.
The Multiple Opening Circulation Sub (MOCS Tool) is a finalist for Best Drilling Technology. The Fishing Agitator™ System is a finalist for Best Well Intervention. Lastly, the AQUA-VESTM Mobile Water Treatment System is a finalist for Best Health, Safety, Environment / Sustainable Development Onshore.
The Multiple Opening Circulation Sub (MOCS Tool) is a circulation bypass sub that, utilizing a unique cycling mechanism design, allows unlimited cycling without the need for multiple ball drops. The tool is cycled in seconds using a single drop ball and changes in flow rate. Short shift times and unlimited cycles allow the MOCS tool to be used for multiple applications down hole, from placement of Lost Circulation Material (LCM) to bottoms-up circulation. The MOCS tool reduces downtime during the use of circulating tools in hole and has been proven to increase efficiency while reducing costs.
Weatherford: It is worth to mention that among many engineered solutions to overcome lost circulation issues, drilling with casing and drilling with liner technologies are the most efficient and reliable. Both are well-known to producing companies for many years. Drilling with casing and liner technologies enable to drill and run, set and cement casing in a single trip, accelerating well construction, minimizing costs, and reducing risk exposure; they also allow drilling through potentially hazardous intervals, such as lost-circulation zones, differential pressure areas and unstable formations. They have been employed in many regions and countries as effective methods of cutting drilling costs by reducing drilling time and mitigating drill-string problems encountered during conventional drilling process. The procedures for rotary drilling with casing are relatively simple, require no modification to the conventional drilling rig package and use conventional oilfield tubular goods. When target depth is reached and circulating bottoms-up is performed, cementing can begin immediately. The system is also extremely reliable, if proper engineering calculations are carried out prior to the operations.
Targin Drilling: We propose:
• Water-based isolating substances (of high filtration to be pumped under pressure, diesel oil / bentonite, cross-linked polymer, diesel oil / bentonite / cement, cement slurry).
• Hydrocarbon-based isolating substances (infusorial silica, calcium carbonate M-I-Х-II, hard plug for hydrocarbon solutions).
• Injection technique for high-viscosity LCM.
• LCM of different fraction and composition, also for production reservoirs.
• Equipment for local strengthening of walls.
7. Can you describe a recent drilling operation that has used your products to successfully reduce or stop lost circulation? Describe the scenario, procedure and results.
Halliburton: Multiple examples can be provided. Multimodal LCM material was successfully used for operations in Bashkortostan to cure total losses. Halliburton was involved 1 month after the incident happened during which multiple technologies by other service companies were applied including swelling polymers, various neutral LCM products and others. It helped stop many days of NPT and the loss of hundreds of cubic meters of drilling fluid. In West Siberian fields, the company has for the past two years successfully employed preventive technology while drilling wells with abnormally low formation pressure with the continuous addition of BARAFLAKE® M to the drilling fluid while drilling the challenging intervals.
National Oilwell Varco: In the region of Buzuluk, a 6 1/2 in. MOCS tool was run in Russia as a BHA protection tool in a lost circulation application. The tool was circulated through for a total of 70 hours, was in bypass mode for nine hours and was cycled 15 times. The MOCS tool cycled more times in this single run than other tools in the market typically can, as the mud loss issues were resolved.
Weatherford: One of the recent jobs performed by Weatherford was application of DwCTM technology, including the Defyer® DPA 4416 drillable casing bit for well drilling in the Russian North and through permafrost reservoirs. There were some challenges to be overcome: to drill sections in three wells of 230-650 m with thief, or lost circulation zones; reduce fluid losses and mitigate wellbore instability while drilling, as well as enhance operational safety and decrease the number of trips. Simultaneous drilling and casing eliminated the need to change the BHA, which reduced the number of trips and limited personnel exposure. Weatherford constructed the intervals in approximately 3.5 days in specific climate conditions.
Drilling-with-Casing was used to isolate lost circulation zones, increase the rate of penetration and minimize wellbore instability. The technology was used in 3 wells, resulting in about 4 mln. rubles savings per well; consequently, surface casing drilling time was reduced by four days on the average, decreasing the wear of equipment and drill pipes.
It shall be noted, that drilling with casing method is especially suitable for northern countries such as Russia, Canada, and Alaska, were severe loss zones in shallow sections pose a significant challenge. The analysis undertaken after completion of the project showed the efficiency of DwC technology, including lower mud losses while drilling through lost circulation zones and lower bridging agent consumption. This once again confirms the advantages of plastering effect.
DwLTM technology has also proved its efficiency in Russia. Due to its simple design and efficiency, drilling with liner was decided to be used by one of Weatherford customers. It is worth to mention that DwL technology enabled completion of 6 wells. A length of open hole interval drilled by a 127-mm liner in one well reached 254 m. Three absorption zones were encountered, but a number of complications while drilling was minimized, and an average well construction time was 20 days per well. It should be mentioned that the average well construction time using conventional drilling methods is 35 days. Notably, the technology of drilling with liner was first applied for drilling “shallow” (sub-horizontal) wells, and problems were overcome thanks to better circulation caused by a streamlined liner design and annulus enlargement. Production casing section was fully drilled. Moreover, as experts stated, with drillable Weatherford bit it will be even possible to proceed with drilling operations below liner in case of sticking.
Targin Drilling: The below technique was used by our drilling mud contractor during a well construction in the Spassk field.
Lost circulation occurred in the depth below 1150 meters and the intensity reached 30 m3/h and higher. Further drilling, down to 1418 meters, was accompanied by measures against lost circulation of varying intensity. In the 522 to 769 m interval (Upper Carbonic) the well allegedly bleeds hydrogen sulfide containing water (1.06 g/cm3). Based on the GIS data the following intervals were detected where lost circulation was the highest: 1184-1190m, 1200-1210 (20) m. Mud loss was 543 m3. The total capacity of packing clay / gel cement / LCM / sawdust was 337m3. The response measures took 41 days.
As a remedial measure it was decided to inject 7 m3 QUICK-STONE.
The injection and drilling-out was successful. The lost circulation intensity was 2-3 m3/h afterwards and it was then possible to proceed drilling and inject additives into the mud.
8. With the market suffering from the low oil price, are “short-cuts” being taken when dealing with lost circulation issues? If so, how does this affect the well, both in the short and long term?
Halliburton: Lost circulation costs operators lots of money. Even at the time of high oil prices some companies tended to save on LCM materials and technologies used. Technology used to combat/prevent lost circulations must be optimized both technically and economically. The LCM approach will likely be in use on onshore projects while the high tech approach will be in demand for offshore and the most challenging onshore projects. I don’t think there is a direct link to oil price.
National Oilwell Varco: We tend to see many operators prefer to save on additional tools in the BHA striving to drive down the costs. However, the rental rate of MOCS is negligible as compared to the potential mud losses or even more aggravated consequences due to full loss of circulation.
Weatherford: In case of hard-to-drill reservoirs where efficient exposure is problematic, with low hydrocarbon prices and relatively high costs of efficient state-of-the-art technologies, it would be reasonable to look for compromise solutions. These may include the combination of conventional and proven technologies for each specific field or formation and new technologies including recent developments. Such approach is applicable to reservoirs with various lithology, but it is especially relevant for highly cavernous and fractured carbonate formations, which feature lost circulation issues.
The selection principle of zonal isolation equipment and drilling technology for borehole stability and optimization of mud flow rates to improve borehole cleaning efficiency and to control annulus pressure with advanced lost circulation materials helps reduce well construction time and improve operational safety – and such approach provides the operator with a set of solutions to be selected based on actual conditions.
Targin Drilling: Today the main goal is to reduce the cost of lost circulation remedial measures. It is also important to remember the controlling factor and to not affect natural permeability. Acid-insoluble LCM placed into the production well may reduce the reservoir characteristics. And we will have quick ESP failure and eventually short time between overhauls.
9. What is the future for technology development within lost circulation – what new products/services can we expect to see in the near future?
Halliburton: Technology is developed to address current or potential challenges. In other words, future technologies will depend on those challenges. If they are similar to what we see now, LCM technologies will likely remain the same. On the other side, if there is significant progress in drilling HTHP wells, deepwater and other wells which require new LCM technologies, new LCM technologies will likely appear. I don’t think though they will differ from existing technologies drastically. I would expect existing technologies with improved features like higher temperature limits, less time for reaction etc. It is also possible that nanotechnolgies will be introduced in the material production industries, e.g. our innovative spongeous material BaraLock®-666 is produced on the same principle as graphene-based materials making them sustainable in reservoir conditions.
National Oilwell Varco: With Western Siberia market shifting towards sidetrack applications, there is 4 1/8” MOCS tool design being the pipeline to step into the new market for NOV. Also, new indexing mechanisms are being developed right at this moment.
Weatherford: It is rather difficult to highlight just one product or tool among advanced developments, because intensive engineering studies are ongoing in engineered chemistry, hydrodynamic pressure management and mechanical isolation of formations. New ideas will keep coming until we find a comprehensive solution.
Targin Drilling: Development of lost circulation preventive measures is our priority. We plan to utilize circulating subs, cross-linking high-adhesive agents, swelling agents and low weight mud (below 1.0 g/cm3, i.e. OBM).
Kharitonov Andrey Borisovich
Halliburton
Kharitonov Andrei Borisovich graduated from D.I. Mendeleyev University of Chemical Technology of Russia. Doctor of Chemistry since 1998. Visiting scholar for 4 years at Hebrew University of Jerusalem, Israel, Department of Organic Chemistry. Author of more than 30 scientific manuscripts in the field of Biochemistry and Analytical Chemistry. Employed by Halliburton since 2003. Currently working as a Technical Manager for Russia and Caspian Areas, Drilling Fluids Division. SPE Member since 2007. Author of more than 15 manuscripts in the field of Oil and Gas well construction.
Roman Che
National Oilwell Varco
Roman Che is a graduate from the Gubkin’s Russian State University of oil and gas (Construction Engineering degree). Since 2009 he has participated in the Next Generation Program and then moved to the Advanced Drilling Solutions department as an Engineer. Roman has held positions of the Drilling Solutions Engineering coordinator, and the Account manager – Far East. He is currently the Drilling Technology Product Line Manager supporting Russia and CIS.
Stanislav Kulikov
Weatherford
Stanislav Kulikov, Ph.D., Project Manager for MPD and DwC, author of about 20 articles and a book titled ‘Nondestructive inspection in Drilling’. He has been holding various positions with Weatherford for over 7 years. Stanislav graduated from Moscow State University of Instrument Engineering and Computer Science as a design engineer in 2006. He has worked in oil and gas industry for over 10 years.
Ilshat Ganeev
Targin Drilling
1994-1999 Ufa State Petroleum Technological University, Oil and Gas Well Drilling
1999-2008 Neftekamsk Drilling Directorate of Bashneft, rising from Assistant Driller to Process Engineer in the Engineering Department
2008-2009 Neftekamsk Drilling Directorate of Bashneft-Geostroy, Process Department Deputy Manager
2009-2012 Neftekamsk Drilling Directorate of Bashneft-Geostroy, Process Department Manager, Chief Process Engineer
2012-2015 Neftekamsk Deep Drilling Expedition of Bashneft-Burenie (Targin Drilling since 2014), Chief Engineer
2015- Current Process Department Manager, Chief Process Engineer in Targin Drilling
