Pernites, Roderick (BJ Services) | Brady, Jason (BJ Services) | Padilla, Felipe (BJ Services) | Clark, Jordan (BJ Services) | Ramos, Gladyss (BJ Services) | Callahan, Jaron (BJ Services) | Garzon, Ricardo (BJ Services) | Sama, Raymond (BJ Services) | Embrey, Mark (BJ Services) | Fu, Diankui (BJ Services) | Johnson, David (Independent Resources Management) | Richey, Nicolas (Independent Resources Management)
Increasing horizontals, narrowing annular gaps, more stringent cement regulations, fracturing with more stages and high pumping rates on top of more cost-efficient well completion are raising demand for lightweight cements, which are designed to prevent damage and lost circulation problems in weaker formations. However, many alternative lightweight materials that are more cost effective than glass beads, which are known to provide superior strength, are increasing waiting-on-cement time, thus delaying further drilling. They also struggle to deliver the required compressive strengths. This paper presents (1) recent case histories of successful field applications of new stronger non-beaded lightweight cement, (2) extensive laboratory data of various field designs with new lightweight cement versus premium commercial lightweight cements, and (3) detailed scientific study explaining how the innovative lightweight cement has provided superior fluid stability and set cement mechanical properties.
The successful field trials occurred in the Permian basin for all four wells on the same pad. About 400 bbl of the new lightweight cement at 10.5 lbm/gal density was delivered to complete each cementing job with 134°F BHST and 6,000-ft measured depth. The four wells were completed with the new lightweight cement, remarkably having no glass beads despite the extremely low density. Unlike the previous job designed with commercial lightweight cement, the new cement has provided far greater compressive strength and has shown faster (18 to 24 hr) strength development. During placement, the new lightweight cement slurry has demonstrated exceptional stability with fewer additives than the previous design, thus simplifying field operations. Multiple laboratory test data at different cement densities (10.5 to 14.5 lbm/gal) for other regions confirmed the enhanced performance of the new lightweight cement in both slurry form and set cement over conventional lightweight technologies. Detailed scientific study via X- ray Diffraction (XRD) explained how the new lightweight cement provided superior set cement performance.
The novelty of this work and invaluable contribution to the industry is the first successful field application of a newly developed micromaterial that provided a lighter, stronger, low-permeability, non-beaded cement that enhances wellbore integrity and provides better zonal isolation. New findings from XRD and Scanning Electron Microscopy (SEM) imaging techniques about the new micromaterial lightweight additive may provide insights for improving the performance of traditional materials.
The development of Early Permian reservoirs in the Fairview Field is limited by highly depleted shallower Bandanna coal seams and naturally fractured formations that would not allow to reach the original geological goals. Offset wells in the area had been executed as three string well design due to long open hole section across depleted Bandanna and multiple loss zones. Multi-stage cementing was required to ensure there is proper zonal isolation. These resulted in significant incremental cost to achieve 5-1/2″ production casing. Through the depletion of upper coals, fracture pressure in these zones has decreased due to reduction in pore pressure.
Drilling in two string design carries higher execution risk due to long open hole section, depleted formations and differential sticking, highly fractured formations, narrow window between fracture gradient and pore pressure, and multiple loss zones which demands special techniques for treatment of loss zones and hole stabilisation while drilling. Considering the downhole conditions, which pore pressure ranging from 2 to 9 ppg in the different formations, the importance of zonal isolation, establishing barriers in aquifers and achieving overall cement coverage is also extremely important.
With introduction of various new LCM products, cement plugs, foam cementing, RCD for drilling with no returns (blind drilling), Santos has achieved major success developing Early Permian fields. This Paper describes how two string design was successfully implemented to drill Early Permian wells. This paper serves as an operational guide to ensure challenging depleted and highly fractured zones can be successfully drilled while minimising risks.
Kolchanov, Petr (Schlumberger) | Perroni, Dominic (Schlumberger) | Medvedev, Anatoly (Schlumberger) | Gao, Yan (Schlumberger) | Tercero, Randy (Schlumberger) | Todd, Larry (Schlumberger) | Lungwitz, Bernhard (Schlumberger) | Cowan, Kenneth Mike (Occidental Petroleum) | Turner, William (Occidental Petroleum)
Currently, hydraulic isolation of wells drilled with nonaqueous fluids (NAFs) relies heavily on the elimination of mud from the annuli before the placement of cement. Failure to expel all NAFs will result in residual fluid channels that will compromise well integrity and can even serve as nonproductive communication pathways during subsequent stimulation treatments. To mitigate this risk, an interactive cementing system is presented that is designed to reduce conductivity of the residual mud channels.
Although mud removal remains an integral part of the cementing process, this new cement formulation was developed to improve zonal isolation in the case of poor mud removal. The unique cement system reacts with the hydrocarbons present in NAFs, leading to a reduction of channel permeability and mobility. This significantly improves the likelihood of hydraulic isolation. Specialized testing protocols were developed to enable the demonstration of the capabilities of this new system. In addition, API testing methods and analytical techniques were used to optimize the slurry.
The development of the new cement system focused on the optimization of the active component concentration to give a favorable interaction with NAF, and at the same time, minimize the effect on cement rheology and mechanical properties. Procedures developed in-house demonstrated that the new system effectively reduces hydraulic conductivity of microannuli as well as channels up to several tenths of inches in size. Zonal isolation laboratory experiments were extrapolated to predict whether the modified channels can withstand the range of differential pressures typically seen between neighboring fracturing stages. This is the most critical operation that the cement sheath would be subject to.
Field tests are on-going at the time of writing this manuscript, and the preliminary results will be presented and discussed in this paper.
Some of the land fields in Middle East contain important potential gas reserves, but zonal isolation of long drilling and production liners have been a challenge. Cementing these long liners along formations with low fracture gradients risks formation breakdowns when exceeding the maximum allowable equivalent circulation densities. Consequences include severe losses, formation damage, and insufficient placement necessitating costly remedial cementing, or even loss of the well.
Many wells in one field were abandoned and not completed because of the tight pore-fracture pressure window, which induced severe losses while drilling the intermediate and production sections. Operators have struggled to mitigate those drilling challenges, and one of the last approaches was to use an ultra-slim hole design; however, this design exacerbated the cementing challenges for the long 7-in. liner. We review this case history and outline the corresponding planning (spacer/cement fluid designs, placement simulations, and lab test results), pre-job practices, and job execution with evaluation.
In this particular well, the 8 3/8-in. open hole section was drilled to the casing point with no losses. However, while running the 7-in. liner (at > 10,000 ft) total losses occurred. A new design approach was developed and applied to mitigate the problems associated with cementing this section. This approach centered on the careful selection and engineering design of a spacer to cure and mitigate induced losses, and the use of high-performance cement slurries. Desirable properties of the latter include very low fluid loss and exceptional fluidity (low rheology) without development of free fluid or sedimentation. Finally the 7-in. liner was successfully cemented, and cement was found on top of the liner after reversing out.
A comprehensive approach on how to cure or reduce lost-circulation problems during cementing operations for critical sections (such as very long liners along fragile formations) are presented and discussed in this study. Case histories from several wells in the area are used to demonstrate the success of this approach with guidelines and lessons learned for similar upcoming projects.
Society of Petroleum Engineers - Copyright transferred to SPE by Larry Moore on behalf of Preston L. Moore.
The challenge was with wells where the casing had lost its barrier/integrity because of casing leakage. There the result was that production wells were closed in. These problems are often caused by cementing failure when the well was drilled and cemented, lost zone, experienced corrosive formation fluid from the formation, treads leakage or other reasons for this integrity failure. There have been tried out serial methods for how this casing leakage can be repaired safely and in a cost-effective manner.
Casing damage/leakage with low or non-injectivity have been squeezed and repaired with Thermal activated resin. Thermal activated resin is a nonreactive polymer with qualities that are resistant to all formation corrosives/hazard fluids. Thermal activated resin will reinstall a good well barrier and integrity to protect casing from future corrosion. Thermal activated resin has been used in serial wells in Saudi Arabia in both onshore and offshore fields. In a small volume, with a controlled setting and short operation time, a high success rate has been achieved.
The solution to these challenges was developed by designing thermal activated resin casing repair liquid plug with a density equal from 64 pcf to 152 pcf. The setting time can also be adjusted accurately. This new treatment slurry was able to be bullheaded and displaced with polymer mud/brine at 64 pcf to 152 pcf. The slurry was easily able to be pumped through the drill pipe. This novel product possesses low elastic modulus and high flexibility in density, viscosity and fast setting time according to requirements. The well barrier elements made of this product have no risk of shrinking, cracking, gas channeling or deterioration upon exposure to harsh reservoir environments.
This paper presents a case history and field application of this novel polymer based casing repair material for successful treatment of full losses or when there is no/low injectivity in formations in most of the critical oil and gas fields in Saudi Arabia. Also, the paper includes a discussion of the methodology, material properties and applications.
Chemical and physical modification of a sustainable, derivatized-cellulose polymer has created a single material capable of replacing several different cement additives. This slowly-hydrating, hydrophilic biopolymer is capable of performing as a fluid loss agent, suspending agent, free water control agent, and extender for use in wells up to 225°F and in some conditions up to 250 °F.
The single, new cement additive effectively and economically replaces separate fluid loss additives, free water control, and slurry stabilizers as well as reduces retarder loadings. Laboratory and field results, operational aspects, and slurry design simplification are conferred in this publication. Standard API test results using Class H ordinary Portland cement slurries with densities ranging from 13.5 ppg to 15.5 ppg including a 14.5 ppg cement blend containing 50% fly ash at multiple temperatures are presented.
The biopolymer works best with the lower and middle density cements. Unlike most fluid loss polymers, this new additive doesn't produce the high initial viscosities, thereby reducing pumping horsepower requirements and equipment wear and tear. A field case in an 18,000 ft horizontal well (8k ft vertical, 10k ft horizontal) confirms the polymer's effectiveness. Preventing fluid loss is critical in maintaining the proper amount of water to give the cement proper density and mechanical properties. Without adequate suspension and free water control, cement particles will settle at the bottom of the slurry resulting in poor zonal isolation. Slurries containing the cellulose biopolymer performed equal to or better than slurries containing multiple, traditional additives. These additives can interact with each other both antagonistically and cooperatively so that a minor change in one can cause unwanted ripple effects to the slurry properties. This makes slurry design complicated and time-consuming. Replacing several of the commonly-used additives with this modified cellulose minimizes and even removes these complicating ripple effects.
The polymer's ability to serve different roles at the same time leads to smaller additive inventories, easier logistics, less time spent on slurry design iterations, and simplified field operations which all add up to improved economics and reduced chance of error during placement of the cement.
Constructing wells in reservoirs with high concentrations of carbon dioxide (CO2) is a challenge in itself. In South East Asia region drilling campaign in a high-CO2 reservoir was made even more difficult because of high well deviation, long production sections, a narrow drilling window, and loss of circulation. Prior attempts to develop the field established that this reservoir would not be easily exploited. One complicating factor was that the reservoir has multiple stacked layers of sand up to 8 zones in each well, These zones have different pressure regimes that are spread out in the reservoir section of average 3,000 meters per well. Effective mud removal is essential to achieve zonal isolation in these wells because mud left behind the cement will likely result in communication between the zones. In order to realize the long-term production plans for these offshore wells, the operator needed a fit-for-purpose cementing solution.
The operator was able to successfully overcome the aforementioned challenges and successfully cement seven wells using a system that incorporate blast furnace slag (BFS). The wells were drilled with a jackup rig in a water depth of 90 m [274 ft]. A cement evaluation log and the absence of sustained casing pressure confirm that there have been no zonal isolation concerns since the first well started producing in November 2013. The BFS system has proven to be cost effective and has the added advantage of being compatible with the existing cementing equipment without any special modifications.
Spaulding, R. (University of Pittsburgh) | Haljasmaa, I. (AECOM-NETL) | Fazio, J. (AECOM-NETL) | Gieger, C. (U.S. Department of Energy National Energy Technology Lab) | Kutchko, B. (U.S. Department of Energy National Energy Technology Lab) | Gardiner, J. (ORISE-NETL) | Shine, J.M. (Baker Hughes Inc) | Benge, G. (Benge Consulting) | DeBruijn, G. (Schlumberger) | Harbert, W. (University of Pittsburgh)
The objective of this paper is to evaluate the dynamic moduli of atmospheric generated foamed cements at varying foam qualities routinely used for zonal isolation during well construction. Mechanical properties of the hardened foamed cement samples, such as Young's modulus (YM) and Poisson's ratio (PR) will be discussed, as well as permeability. All of these properties were obtained as a function of cyclic confining pressure ranging from 12 - 52 MPa (1,740 – 7,540-psi). The dynamic parameters were derived from ultrasonic velocity measurements, while permeability was measured using the transient method. Stepwise loading and unloading schedules were conducted to test the permeability and mechanical properties of the foamed cement at simulated wellbore conditions. Applied pressures varied between 6.5 MPa (943 psi) to 46.5 Ma (6,744 psi) in 4 MPa (580 psi) increments in two full up/down cycles. At every increment during these cycles, ultrasonic compressional (P), fast shear (S1), and slow shear (S2) wave velocities were measured, as well as the samples’ response to the upstream sine pressure wave of approximately 0.5 MPa amplitude. From the sonic velocity data the dynamic moduli including YM and PR were calculated, while the sample's response to the pressure wave was used for permeability calculations. Observations of both neat and foamed samples reveal variations in YM as well as changes in the other properties and characteristics. Differences were observed between the foam qualities, depending on the parameter being assessed. This information should enable design contingencies and allow for more resilient designs of foamed cements when used during well construction. In addition, industry can use these results as a baseline for comparison with previous, current, or future work including recently acquired field-generated foamed cement samples (
Lost circulation or total loss of drilling fluid or cement slurries in the cavernous formation, permeable zones and natural/induced fractured zones during the drilling and/or cementing operation can be an expensive and time-consuming problem. The consequences of lost circulation could be from the possibility of a blowout to the complete loss of well. Typical solutions for lost circulation has been a pill containing in-soluble materials like platelets, fibers or sized particulates. However, such in-soluble or non-removable materials can cause permanent damage to the producing zones by plugging pores due to in-soluble fines migrations. In some cases, plug dislodgment the can cause premature return of the lost-circulation itself.
This paper describes the results from our laboratory development of two different kind of acid soluble cement systems namely (a) traditional Portland cement based system with appropriate amount of CaCO3 and (b) Magnesium-Oxychloride-Cement (MOC). In both these systems, sized CaCO3 has been used to enhance the bridging effect at highly permeable formations. In addition, we have carried out extensive research to optimize the final set cement compressive strength by optimizing particle size distribution of CaCO3. In addition to bridging capabilities, these fluids can be foamed to enhance the capability of preventing severe lost circulations. Quick setting and 100% acid solubility properties of the MOC systems is the key for minimizing the damage of the producing zones from fines plugging and/or deeper invasion. Laboratory results such as thickening time, compressive strength, and rate of acid solubility will be discussed to compare these two systems in terms of their application pros and cons. In addition, other plausible applications for such acid soluble settable systems will be discussed for both oil and gas wells as a temporary plugging materials.