Poor Cement Research Articles

The geological constraints of the development of sandstone landforms in Central Europe, a case study of the Świętokrzyskie (Holy Cross) Mountains, Poland

Eighty sites of crag groups and individual crags occurring in the Świętokrzyskie (Holy Cross) Mts., upland situated in central Poland, were described in detail in order to examine the lithological, structural, mechanic properties and the tectonic features of sandstones and quartzites representing six crag-forming lithostratigraphic units: Cambrian quartzites, Devonian quartzitic sandstones, Triassic and Jurassic sandstones. Specific features of these rocks are: their occurrence within the sequences consisting of different rock series, high energy depositional environments and siliceous composition. The cragforming rocks differ in the amount of cement (from strongly cemented quartzites to very porous sandstones with poor cement), which determines the diverse mechanical properties (from very strong to friable rocks). The crucial feature enabling formation of crags built of porous and friable sandstones is very dense grain packing due to chemical and mechanical compaction. Regarding the principal role of the gravitational disintegration of rock massifs under the periglacial conditions in the Late Pleistocene, other factors constraining the crag formation and shaping are: the tectonic situation of rocks (the orientation of strata and joints) as well as adequate joint spacing and bed thickness. Petrographic, structural and tectonic features are interrelated.

A Wellbore Stability Model for a Deviated Well in a Transversely Isotropic Formation Considering Poroelastic Effects

To analyse wellbore stability phenomena when drilling through a transversely isotropic formation such as shale, a wellbore stability model is developed based on the coordinate transformation method and complex variable elasticity theory. In order to comprehensively consider the anisotropies in the transversely isotropic formation, the model includes the followings: 1. the elastic anisotropy due to the sedimentation effect and naturally developed fractures and 2. the strength anisotropy due to the poor cementation between bedding planes and natural fractures. The model is further generalized by accounting for an arbitrary wellbore trajectory under an arbitrary in situ stress orientation. Next, the model is used in a parametric study that includes factors such as elastic anisotropy, strength anisotropy, multiple weak planes, in situ stress anisotropy, and poroelastic anisotropy, all of which can have a great influence on wellbore stability. Finally, a correction for a frequently used failure criterion has been made to ensure that the newly developed model is comprehensive and accurate for wellbore stability analyses in highly heterogeneous formations.

Primary hybrid THA using a polymethyl methacrylate-precoated stem: A single-center experience with a 10-year minimum follow-up.

The high failure rate of cemented femoral components in the 1970s facilitated the improvement of the cementing technique and surface finishes such as polymethylmethacrylate (PMMA)-precoated stems, reporting a survival rate of >95% at 10 years from some studies. However, controversy persists regarding whether precoated femoral stems are associated with a longer revision-free prosthesis survival. The purpose of this study was to evaluate the clinical and radiological outcomes of PMMA-precoated femoral stems, and analyze factors associated with implant survival. We retrospectively reviewed 73 primary hybrid total hip arthroplasties performed using PMMA-precoated femoral stems. The mean age of the patients was 61 years. During the mean follow-up period of 13 years, 18 hips (24.7%) underwent aseptic loosening, and all of the loosened stems were subjected to revision surgery 8.8 years (range 4.6-15.5 years) from the index surgery. Younger age and poor cementing were significantly associated with aseptic loosening (P = 0.013 and P < 0.001, respectively). However, the aseptic loosening rate was also high at 13.1% even with a good cementing technique. In conclusion, the PMMA-precoated stem failed to show expected advantages and needs to be replaced with other surface finish stem designs. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1300-1306, 2017.

Imaging By Multiples: A Case study in the Carnarvon Basin

Vertical Seismic Profiling (VSP) is renowned for its high resolution images of the subsurface. By and large, the images derived are beneath the well. Now a new technique allows imaging above the borehole by utilizing free surface multiples as a secondary source. A number of conditions need to be met for this technique to successfully meet its objectives. This paper presents a case study of data acquired recently in the Carnarvon basin and processed to derive an image above the well. The high-resolution, multiple-free VSP image allows verification of the shallow part of the subsurface. This information can be used to identify drilling hazards, faults and generally improve subsurface interpretation. The result can also be used to overcome the limitations of poor cementing which often causes casing ringing noise, which in itself is detrimental to VSP imaging. Subsequently, the size of the VSP image for this survey was increased by a factor of 2, thus greatly improving the value of acquisition.

Clinical Evaluation and Patient Satisfaction of Single Zirconia-Based and High-Noble Alloy Porcelain-Fused-to-Metal Crowns in the Esthetic Area: A Retrospective Cohort Study.

The aim of this study was to assess clinical survival, complications, and patient satisfaction with single zirconia-based crowns (ZC) or high-noble alloy PFM crowns (HC) in esthetic areas. The study was a retrospective cohort study with up to 3.8 years follow-up (mean 2.5 years). Patients who met the inclusion criteria were reviewed. Survival rates, complications, satisfaction rates (color and form), and overall satisfaction (visual analogue scale, VAS) were evaluated by follow-up examination. Chi-square test (survival, complication, and satisfaction rate) and unpaired t-test (overall satisfaction: VAS) were used to test the difference between the ZC and HC groups. Survival rates and complications were assessed both at subject-level (patient as statistical unit) and at tooth-level (tooth as statistical unit). One hundred and thirteen patients met the inclusion criteria; 95 patients (ZC: 45, HC: 50) with 132 crowns (ZC: 61, HC: 71) were enrolled in the study. The overall survival rate was 93.3% for ZC crowns and 96.0% for HC crowns at subject-level and 93.4% for ZC crowns and 97.2% for HC crowns at tooth-level (p = 0.56 and 0.30, respectively). Veneer chipping was the most frequently seen complication. One HC crown lost retention because of poor cementation. One patient in the ZC group showed progression of periodontal disease. No significant difference of complications was found between the two groups at subject-level and tooth-level (p = 0.37 and 0.34, respectively). The overall satisfaction (VAS) was 8.18 for ZC crowns and 8.46 for HC crowns (p = 0.34). The results of the study showed that a high survival rate could be achieved in both ZC and HC groups. Chipping of the veneering porcelain was the most frequently seen event that led to short-term (less than 3 years) failure and complications. The patients' rating of ZC crowns was not superior to HC crowns. Well-designed studies with high evidence level and large sample size are still needed to further explore the clinical success of ZC and HC crowns.

Energetics Applications for the Oil and Gas Industry

Energetics Applications for the Oil and Gas Industry

Plate failure following plate osteosynthesis in periprosthetic femoral fractures.

Increasing numbers of total knee and hip arthroplasties result in a growing number of periprosthetic femoral fractures (PPFF). PPFF with a stable stem component are treated commonly with plate osteosynthesis. Therefore plate failure is seen as a major complication. The aim of this retrospective study was to investigate the patients' outcome after plate failure. The database of a Level 1 trauma center was searched for all patients treated for a PPFF with plate osteosynthesis. Patients with plate failure were investigated specifically. Standard demographic data, details on initial arthroplasty, trauma, and treatment were recorded for all patients. All fractures were classified and their outcome reviewed. Seven (8.8%) out of 80 patients treated with plate osteosynthesis following PPFF met our inclusion criterion being plate failure. All these patients were female, with an average age at primary surgery of 74 ± 13 years and a mean follow-up of 885 days (range, 264-2549). Four patients suffered a PPFF after total hip arthroplasty (THA) (2 Vancouver Type B1 and 2 Type C) and three after total knee arthroplasty (TKA) (Lewis-Rorabeck Type II). Following plate failure, four patients healed uneventfully and three patients experienced complications such as pseudarthrosis, screw loosening, and further plate failure. In patients with poor bone quality, bone graft, bone cement, and bone biologics have to be considered in revision surgery. Furthermore, long-stem revision and tumor prosthesis are an additional solution.

Characteristics of the Sanmen Formation clays and their relationship with loess landslides in the Guanzhong area, Shaanxi, China

Large, deep-seated landslides are one of the most common geologic hazards in the Loess Plateau of northwestern China, especially in the Guanzhong area of Shaanxi Province. To understand why these landslides occur, we conducted a field investigation, remote sensing image interpretation, and physical and mechanical tests. Geologic surveys have shown that the landslide deposits are composed of thick loess, river terraces, and the Pliocene Sanmen Formation and that the rupture surface is located in the Sanmen Formation clay. Test results suggest that the Sanmen Formation material has a high clay content (particle diameters < 1.95 μm) and a substantial proportion of expansive clay minerals such as smectite or illite-smectite. In addition to high activity and high water content, the clay is also characteristically weak with poor cementation and high expandability. The peak and residual strength values exhibit large differences under natural and saturated states. It is inferred that the strength of the Sanmen Formation clay greatly decreases when infiltrated by underground water. The clay then becomes a weak layer which forms shear zones. These shear zones are what control the development and distribution of landslides along the edge of the Loess Plateau. This study is important for understanding the occurrence of large-scale loess landslides and assessing urban natural hazards in the western Guanzhong area of Shaanxi.

Technology Focus: Well Integrity (January 2015)

Technology Focus Cementing operations represent one of the more critical aspects concerning well integrity. Despite the large amount of research and the huge number of operations throughout the years, the industry still faces well-integrity problems during and after cementing operations. These occurrences have been experienced by the petroleum industry worldwide and can happen at any moment of the well life cycle, from the drilling phase to abandonment after the well’s production life. Here, I have categorized these well-integrity issues according to the moment at which they manifest: during the cement displacement inside the well (minutes); after the cement placement (hours to days), and after the cement has been cured (months to years). The first category may result in serious well-control problems, including blowouts (the Macondo blowout was related to cementing operations). According to a survey published by the former Minerals Management Service, during the period between 1992 and 2006, the leading factor contributing to blowouts in the US offshore area was cementing (18 out of 54 blowouts reported). These well-control problems are normally caused by improper design of the cementing operation in terms of hydrostatic pressure of the cement slurries or preflushes, failure when mixing the cement slurry to achieve its planned density, lost circulation during the cement displacement, or failure of casing float equipment. In my opinion, well-control courses must dedicate more time to discussing well-control problems during cementing operations. The second category encompasses those issues normally associated with the loss of hydrostatic pressure of the cement slurry during its initial hydration period and consequent gas flow inside the annulus. This condition also can cause well-control problems, pressure buildup in the annulus between casing strings, and zonal-isolation problems later on. The industry has several ways to mitigate these occurrences that include, but are not limited to, the use of gas-block additives, the design of cement slurries with short transition times, the application of surface pressure on the annulus, the use of external casing packers, and the implementation of multistage cementing operations. Despite the application of these mitigation measures, annular gas flow after cementing is still a recurrent problem, and remedial solutions are normally expensive and difficult. The last category refers to long-term problems normally caused by poor cementing practices, with detrimental effects on zonal isolation. Inadequate drilling-mud removal during the cement-slurry displacement in the annulus, insufficient cement height that may lead to casing leakage and corrosion problems, and the channels that result from the gas flow previously mentioned are some of the factors that can contribute to long-term well-integrity failures. Again, remedial solutions are normally expensive. JPT Recommended additional reading at OnePetro: www.onepetro.org. IPTC 16592 Mitigation of Deepwater Shallow Hazards With Simplified Cement System: South China Sea Case Study by Todd B. Ellis, Baker Hughes, et al. OTC 24369 Well-Integrity Analysis Applied to Workover Prediction by T.C. da Fonseca, Petrobras, et al. SPE/IADC 163474 Automated Alarms for Smart Flowback Fingerprinting and Early Kick Detection by Tarab H. Ali, Baker Hughes, et al.

Investigation and remediation of active-clay contaminated sepiolite drilling muds

Unconventional gas and oil development has gained remarkable attention in recent years. However, the high content of active clays in shales makes drilling difficult. Since most formations drilled for oil and gas exploration are shales, active solid dispersion into the drilling mud is a common problem. This might results in severe problems, such as stuck pipes, circulation loss, excessive torque and drag, inadequate cuttings transport, poor log quality, poor primary cement job, and borehole instability.In this study, active clay contamination effects on sepiolite drilling muds were experimentally investigated for hostile drilling conditions. Rheological properties of both unweighted and barite-weighted sepiolite drilling muds with and without sodium chloride additions were tested at ambient to 204°C temperatures. Filtration loss properties were determined at a 0.689MPa pressure differential. The drill-hole cleaning efficiency of sepiolite drilling muds was investigated too. Methylene blue tests were also performed to determine the tolerance of sepiolite muds to solids accumulation.Major findings of this study inferred that sepiolite drilling muds formulated in a certain mixing order of additives provided effective rheological properties and water loss. Acquired results of methylene blue test and sufficient annular velocities for all samples strongly supported availability of these muds against active-clay contamination which is the special emphasis of this study. This is also particularly important for expensive high-angle and extended-reach wells.

Using Taguchi and ANOVA methods to study the combined effects of drilling parameters on dynamic barite sag

Abstract The settling of barite particles in drilling fluids under no-flow conditions and under flow conditions is still a major problem in drilling. The separation of barite particles out of the drilling fluids causes a variety of problems, such as stuck pipe, lost circulation, and poor cement jobs. Furthermore, several severe well-controlled incidents have been caused by barite sag. This paper presents the quantitatively combined effects of the drilling parameters on dynamic barite sag in oil-based drilling fluids. The drilling parameters include annular velocity, pipe rotation, inclination angle, and eccentricity. Two levels for each parameter were considered to develop the test matrix in this study. For example, the parameter of inclination angle has two levels including concentric drill pipe (e=0) and eccentric drill pipe (e=1). The Barite Sag Flow Loop (BSFL), which utilized a coriolis mass flow meter to measure the circulating density of the fluid, was used to conduct tests. The Taguchi method was used to design the test matrix, which greatly reduces the number of experiments required and offers the optimum settings of the control parameters. Based on the two levels of the analyzed parameters, the annular velocity and pipe rotation contribute almost 60% and 21%, respectively, to the prevention of sag. The results also indicate that changing the inclination angle in the range from 60° to 45° from the vertical has the least impact on the prevention of barite sag. The results of this study enable drillers and designers to operate and design wells with fewer problems related to barite sag.

Inherently safer sustained casing pressure testing for well integrity evaluation

This paper presents the use of a model to predict sustained casing pressure (SCP), from early pressure buildup data, as a basis for inherently safer well integrity testing. Inherently safer principles aim to eliminate or reduce the hazards by design rather than by using protective features. SCP, a well integrity issue exhibited in many wells, is any measurable pressure that rebuilds after being bled down and attributable to causes other than artificially applied pressure or temperature fluctuations in the well. Intrusion of gas, resulting in SCP, can occur because of poor cement bond in the casing or cement deterioration. Gas entering the annulus migrates to the wellhead and represents a hazard due to increased wellhead pressure and the gas inventory. Compromised well integrity can have catastrophic consequences on both environmental and safety aspects.Most regulations require the monitoring, testing and, eventually, the elimination of SCP. However, test data analysis is predominantly qualitative and limited to arbitrary criteria. Due to the high percentage of wells that present SCP, accurate, safe and preferably fast testing methods are needed. This paper implements an analytical model, rooted in the transport processes and thermodynamics of the system, to predict pressure profiles and gas accumulation during SCP testing from early-time pressure buildup data. The amount of gas accumulated during different testing criteria, being 1) current practices and 2) early diagnostic by the analytical model, is calculated and compared. Results show that using the analytical model as a predictive tool, testing time is reduced significantly, thereby limiting the amount of gas accumulated and reducing the risk. This makes the testing procedure inherently safer as well as less time consuming.

Assessing Wellbore Integrity in Sustained-Casing-Pressure Annulus

Summary Sustained casing pressure (SCP), exhibited by many wells, is defined as any measurable casing pressure that rebuilds after being bled down, attributable to cause(s) other than artificially applied pressures or temperature fluctuations in the well. Gas leakage, leading to SCP, may occur through the poor cement bond between the casing and the formation, packer, and/or the casing itself. All safety regulators require SCP elimination. However, test-data analysis is mostly qualitative and limited to arbitrary criteria, thereby lacking consensus. This paper attempts to provide a theoretical frame and a model for quantitative analysis of SCP-test data. Specifically, we adapted a model for SCP that is rooted in the transport processes of the system. The model accounts for mud compressibility and assumes gas is leaking into the annulus and migrating up the annular liquid column. Some robust assumptions about the transport processes allow for expressing the governing equation as a first-order, linear differential equation that is solved with appropriate boundary conditions. The resulting algebraic expression for the casing-pressure rise (Annulus A) with time is easy to apply. A comparison of the performance of the model with field data suggests that gas influx causes a casing-pressure (Annulus A) increase in wells.

Investigation of borehole stability in poorly cemented granular formations by discrete element method

Abstract Behaviour of poorly cemented formations in case of drilling a vertical exploration borehole will be studied to achieve an in-depth understanding of borehole stability problem. Analysis of the granular formation behaviour has a significant importance in identifying stability issues, designing adequate borehole supports and choosing an efficient drilling method. This paper presents numerical investigations on the behaviour of poorly cemented formations in the vicinity of an unsupported vertical cylindrical borehole. Due to poor cementation and therefore granular behaviour of these formations, Discrete Element Method (DEM) was identified as being well suited for developing realistic models. To conduct the numerical studies a cube of 8 m 3 made up of spherical particles with diameters ranging from 5 mm to 70 mm was constructed and analysed in three-dimensional Particle Flow Code ( PFC 3 D ). It is a discontinuum code used in analysis of the granular materials where the interaction of discrete grains is considered. A cylindrical opening with the diameter of 0.3 m runs along the central vertical axis of the cube simulating the presence of a borehole. The stresses applied to the cube simulate the underground conditions around an exploration borehole at the depth of 80 m. The effects of in situ stresses around the borehole, strength of particle bonding and fluid flow pressure on the stability of the formation around the borehole have been investigated. It has been shown that the development of in situ stresses in the ground due to drilling a borehole results in the formation of a plastic zone around that borehole. When there is lack of sufficient bonding between the sand grains, the interaction between them results in their movement towards the borehole opening and thus eventuates the collapse of the borehole wall. Furthermore, the presence of high pressure water flow expedites the process of the borehole collapse.

The Effect of Weight Material Type on Barite Sag Tendency

Settling of weight materials is a phenomenon that occurs in high-pressure formations where a high mud weight is needed. Barite sag is roughly defined as the change in density due the settling of weight materials that observed when circulating bottoms up following operations such as tripping pipe where the mud has not been circulating for an extended period of time. This may lead to problems such as lost circulation, well control difficulties, poor cement jobs, and stuck pipe in oil industry. In deviated wells, the settling distance to the lower side of the wall is small in comparison to vertical wells. This leads to rapid generation of solids beds and consequently, sag problems are particularly severe in deviated wells. The authors present the settling rate of different weight materials in muds with mathematical method. Furthermore, it investigates the effect of weight material type and hindered settling factor on settling rate. Moreover, the type of weight materials for barite sag management is recommended.

Method of mitigating the surface erosion of a high-gradient mudstone slope in southwest Taiwan

Soft mudstone dominates the rock mass at southwest Taiwan. Mudstone slakes significantly when it meets water due to a short diagenetic period and poor cementation. Gulleys are visible on the surface of mudstone slopes after rainfall. The low slaking durability resistance of the mudstone causes not only geographical badland but also erosion problems on the highway slopes in the mudstone area. An effective countermeasure for protecting the mudstone slope must contribute to a reduction in surface erosion; facilitate drainage from the slope surface during rainfall; and incorporate a high-strength structure to fight against swelling stress, preserve vegetation, and contribute to slope stabilization. In this study, a new slope erosion countermeasure, the soil-tyre-vegetation method (STV), was applied to an excavated mudstone slope in southwest Taiwan. STV utilizes waste tyres, H-beams, and geotextile. Waste tyres are good for preserving the soil for vegetation on mudstone slopes, mitigating slope erosion. The H-beams support the weight of the vegetation and the soil-filled tyres. The geotextile prevents the loss of fine-grain soil and guarantees drainage from the slope during heavy rainfall. The experimental results for a mudstone slope with a slope angle of 45° showed that STV protected the mudstone slope and improved the condition of the vegetation on it.

Triaxial creep tests of weak sandstone from fracture zone of high dam foundation

The lithology of fracture zone which was developed at the dam foundation of a hydropower station is weak sandstone with poor integrity and pore cementation contact. Its creep properties have a significant impact on the deformation and stability of the dam. Based on the characteristics of loose organizational structure, high moisture content and poor mechanical properties, the triaxial compression tests and creep tests were carried out, respectively. The results show significant non-linear, low strength and no obvious strength peaks. Both axial and lateral strains are achieved more than 3% when the tests are failed. The weak sandstone has a significant creep property, but only transient and steady state appear under low stress. Increased stress causes creep intensified and lateral strain gradually exceeds axial strain. In the failure stage, it has characteristics of large axial plastic deformation, obvious volumetric ductility dilation and large steady creep rate. The accelerated creep appears shortly after transient loading under confining of pressures 1.0 MPa and 1.5 MPa. Therefore, an improved Burgers creep model considering the non-linear characteristics of weak sandstone is built based on hyperbolic equation and the creep parameters are identified. This model can well describe the creep properties of weak sandstone.

Practice of Fuzzy Ball Cementing Pad Fluid in Leakage Zone of Naiman Well N-X-Y

This paper has analyzed the geology and engineering factors of poor cement quality in leakage zone of Jiu Fotang Formation in Naiman Block. Lab evaluation shows that the value of YP/PV of Ceram site-weighted fuzzy ball pad fluid is more than 1.0Pa/mPas, cuttings recovery rate is 94% and bearing pressure is more than 5MPa. 10m3 of pad fluid was pumped to the leakage section of 2310-1865m of Jiu Fotang formation in the well N-X-Y, and pump pressure decreased slightly from 3.8MPa to 3.6MPa and so was the return to surface. However, for this severe leaking zone, this leakage can be accepted. Cement quality was evaluated as acceptable by logging. The problem of cement slurry leakage was solved by fuzzy ball pad fluid and cement quality was improved, so the remedial measure for trial production test was skipped, and then the job cost was reduced and the application of fuzzy ball was also broadened.

Groundwater Protection and Unconventional Gas Extraction: The Critical Need for Field‐Based Hydrogeological Research

Unconventional natural gas extraction from tight sandstones, shales, and some coal-beds is typically accomplished by horizontal drilling and hydraulic fracturing that is necessary for economic development of these new hydrocarbon resources. Concerns have been raised regarding the potential for contamination of shallow groundwater by stray gases, formation waters, and fracturing chemicals associated with unconventional gas exploration. A lack of sound scientific hydrogeological field observations and a scarcity of published peer-reviewed articles on the effects of both conventional and unconventional oil and gas activities on shallow groundwater make it difficult to address these issues. Here, we discuss several case studies related to both conventional and unconventional oil and gas activities illustrating how under some circumstances stray or fugitive gas from deep gas-rich formations has migrated from the subsurface into shallow aquifers and how it has affected groundwater quality. Examples include impacts of uncemented well annuli in areas of historic drilling operations, effects related to poor cement bonding in both new and old hydrocarbon wells, and ineffective cementing practices. We also summarize studies describing how structural features influence the role of natural and induced fractures as contaminant fluid migration pathways. On the basis of these studies, we identify two areas where field-focused research is urgently needed to fill current science gaps related to unconventional gas extraction: (1) baseline geochemical mapping (with time series sampling from a sufficient network of groundwater monitoring wells) and (2) field testing of potential mechanisms and pathways by which hydrocarbon gases, reservoir fluids, and fracturing chemicals might potentially invade and contaminate useable groundwater.

Technology for Improving Life of Thermal Recovery Well Casing

In steam injection process, casing is heated by steam, the change of casing temperature produces thermal stresses in the casing, the casing deforms when stresses exceed the yield point of its material. Casing failure is becoming increasingly prominent in thermal recovery wells, which severely restricts the development effect of such reservoirs, improving casing life of thermal recovery well has become a urgent problem to be solved. Through on-site survey and analysis, reasons for casing damage were determined as follows: strength change by high temperature, sand flow over of oil formation, poor cementing, unfavorable heat insulation and bad material for casing. In order to improve casing life, the supporting measures are introduced, the measures include pre-stress cementing technology, using casing head, thermal stress compensator, high-performance insulation tubing, high temperature cement slurry system, FRT110H special casing, and early sand control completion technology. Field application of these measures has gotten better effect in Shengli oilfield in recent years, the damage rate of thermal recovery well has decreased obviously, and this can provide reference for the efficient development of similar reservoirs at home and abroad. Key words : Casing failure; Thermal recovery wells; Special casing; Cementing; Sand control completion