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ABSTRACT This paper presents an investigation of several slurries using field and laboratory prepared drilling fluids solidified with Blast Furnace Slag. The data presented includes base mud properties, final slurry composition, and slurry properties. This investigation includes measurements of the common properties of thickening time, compressive strength, free water, etc. It also includes an evaluation of the bulk shrinkage ot the set material, shear bond, etc., as well as rheological compatibility studies of the finished slurries with the base muds. These additional tests are considered critical in the potential application of this process under field conditions. Results of large scale bond log tests are included. One of the main benefits from any mud solidification process is the reduction in the environmental impact. The benefit is due solely to the reduction of the volume of mud disposal requirements. Due to the dilution requirements of the mud for the incorporation of the Blast Furnace Slag, the actual volume of mud that can be "saved" from disposal may be considerably less than that reported. This study evaluates the actual reductions in disposal volumes while accounting for the dilution volumes. Economic comparisons from field operations are included as well as a theoretical comparison for zero discharge areas like Mobile Bay. Operational considerations and the economics of required mud isolation and storage are reviewed. From the laboratory data evaluated, environmental, and economic evaluations, it is apparent the use of Blast Furnace Slag slurries for oil field applications must be carefully evaluated on a per case basis. While the process may be a viable mud solidification process, the replacement of Portland cement by this material may compromise some properties considered essential in a cementing operation. INTRODUCTION For this investigation, three typical field muds were chosen. The muds were taken from wells representing various parts of the drilling process. An 8.8 lb/gal lightweight spud mud typical of surface holes, a 12.6 lb/gal mud often seen at intermediate casing points and a 17.6 lb/gal mud representative of the final stages of a well were used as the base muds for this study. The mud properties for each mud are listed in Table 1. Blast Furnace Slag (BFS) slurries were prepared for each of the muds. A temperature of l85°F BHST was chosen for the investigation as this is typical for a 10,000 ft well (with a 1.1 temperature gradient) in the Gulf of Mexico. The aim was to prepare a BFS slurry that would give three to five hours of thickening time at 150°F BHCT. The formulations used for preparing the BFS slurries are found in Table 2. Note that the BFS concentration is expressed in pounds of BFS per finished barrel of slurry. In earlier investigations it is not clear whether the BFS was added to a barrel of diluted mud or was expressed as pounds per finished barrel. If the concentration of BFS is expressed in pounds of BFS added to a barrel of mud, the apparent concentration is higher. This is due slmply to the additional volume taken up by the BFS. For example, in this study Mud 5 has 300 lb BFS per finished barrel or 428 lb added to a barrel of diluted mud.
- North America > United States > Texas (0.28)
- North America > United States > Gulf of Mexico > Central GOM (0.24)
Optimization of Lead Cement Slurry for Use on Utica Deep Intermediate Casing Strings
Winegarden, Jason Alex (NexTier Completion Solutions) | Thomas, Tyler Robert (NexTier Completion Solutions) | Solomon, Marvin Vincent (NexTier Completion Solutions) | Townsend, Douglas Eric (NexTier Completion Solutions) | Algadi, Otman (NexTier Completion Solutions)
Abstract The depth of the Utica formation poses many challenges during drilling operations. In Belmont, Jefferson, and Monroe counties of Ohio, lateral sections are often drilled with mud weights from 13.5 to 15.5 lb/gal. To support these mud weights, the various loss and flow zones encountered above the pay zone must be isolated by a deep intermediate casing. This paper describes the process of optimizing a cement slurry that is light enough to be circulated to surface in a single stage but also has additional properties to ensure that the potential corrosive formations are properly isolated and the casing has long-term protection from damage. The process compares the properties of four cement slurries in the 12-to-12.5lb/gal density range. Conventional tests were performed on each slurry (thickening time, free fluid, fluid loss, and compressive strength). Linear expansion tests determined whether the slurries would be capable of providing a long-term seal, against both formation and casing, to mitigate gas migration and annular pressure buildup. In addition, the team performed initial permeability tests for each slurry. Single-stage jobs were executed using three of the four newly formulated slurries, and this paper presents the success of those jobs as well.
- North America > United States > Ohio (0.55)
- North America > United States > West Virginia (0.34)
- Well Drilling > Drilling Fluids and Materials > Drilling fluid selection and formulation (chemistry, properties) (1.00)
- Well Drilling > Drilling Fluids and Materials > Drilling fluid management & disposal (1.00)
- Well Drilling > Casing and Cementing > Cement formulation (chemistry, properties) (1.00)
- Well Drilling > Casing and Cementing > Casing design (1.00)
Abstract The application of salt for primary cementing in the past has been restricted largely to salt formations. Recognition of its value in cementing through fresh-water-sensitive shales and bentonitic sands has recently brought about wide usage. Formations of this latter type from different areas have been sampled and tested for the applicability of salt cement with emphasis s on improved cement-formation bonding and minimization of formation deterioration by water contact. Field surveys indicate this economical additive has helped to reduce remedial work and to greatly improve the success of primary and squeeze cementing jobs. A study has also been made of the effects of various concentrations of salt in cement systems and how these concentrations modify their slurry properties. Introduction The application and use of sodium chloride in oilwell cementing dates back over a decade. The initial recorded use of salt with cement appeared in the completion of wells through salt domes along the Gulf Coast in the 1940's. In the absence of bulk blending facilities, salt was added to the mixing water prior to mixing with cement. This practice was followed to help provide better bonding to salt formations, as illustrated in Fig. 1. Here it can be seen that the fresh-water slurry has dissolved a portion of the salt, resulting in no bonding between the two, while the salt-saturated slurry causes no solution problem and permits contact and bonding of cement and salt. The addition of sufficient sodium chloride to provide a saturated solution for mixing cement required considerable time and expense to the operator. Foaming, which was encountered during the mixing of salt water, necessitated development of anti-foam agents and it became fairly common to add 1 pt of tributylphosphate/10 bbl of salt water to minimize this nuisance. These operational difficulties and misunderstanding of the effect of salt in cement systems probably account for the long delay in widespread use of such slurries. Another application of brines for mixing cement occurred when early cementers found that certain shaly formations could be more effectively squeezed when using water from the producing zones. However, the addition of salt to the mixing water for this specific application was rarely considered, and only scattered uses are recorded. Perhaps the earliest significant use of salt cement appeared in the Williston basin area of North Dakota and Montana. The problem of collapsed casing and tubing in salt sections and investigation of the reasons for this made it a logical consideration. Here the application was to provide good bonding to salt sections. Previous developments in blending equipment made the dry blending of salt with the cement practical for the first time. Tests revealed that granulated salt added to the dry cement in sufficient quantity to saturate the mixing fluid was a practical approach to overcome previously objectionable features. Wellhead sampling showed that the mixing provided by pumping equipment resulted in solubilization of the salt before entering the wellhead. Today, practically all salt used in oilwell cementing is dry-blended with cement before delivery to the wellsite. In studying troublesome and often expensive squeeze jobs in shaly zones, salt cement was again given consideration. Success with squeeze cementing in shaly sections in Southern Oklahoma might be considered the initial application of salt slurries for shales and bentonitic sands. The use of salt has many unique properties for oilwell cementing. Ludwig described the general effects of salt on cement and the basic chemistry involved when cement reacts with sodium chloride in concentrations ranging up to saturation of the mixing water. More recently, Beach recognized the benefits of small quantities of salt in gel cements. Salt produces two opposite effects on the setting of cement, depending on the concentration. JPT P. 187^
- North America > United States > Texas (0.97)
- North America > United States > Oklahoma (0.66)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (1.00)
- Geology > Mineral > Halide > Halite (1.00)
- North America > United States > Texas > Anadarko Basin > Red Cave Formation (0.99)
- North America > United States > South Dakota > Williston Basin (0.99)
- North America > United States > North Dakota > Williston Basin (0.99)
- (5 more...)
Abstract In deepwater Gulf of Mexico, the use of synthetic-based drilling fluids (SBM) is common practice in all types of wells drilled by different operators. These fluids have been under constant development in past years. However, even with the latest in SBM technology, cementing operations can be adversely affected when this type of fluid is used, which can compromise the quality of the cement jobs. One of the challenges faced is the rheological incompatibility between the cement slurry and the SBM. This may lead to issues such as induced losses during primary cementing operations, due to higher friction pressures, or stuck pipe during plug placement, among others. The higher friction pressures during cement placement in primary jobs can also lead to an inaccurate or inconclusive post-job evaluation when attempting to match software-simulated pressures with actual pressures acquired during the jobs. Despite the use of mechanical separation and spacers, the post-job analysis of several recent cement jobs suggests that contact between cement slurry and drilling fluid is often still occurring. As expected, this contact is most frequently occurring in the annular space wherein there is typically an absence of mechanical separation. In these jobs, laboratory test results using mixtures of slurry and SBM with various ratios have shown levels of incompatibility, which have been correlated to evidence of higher-than-expected friction pressures in the same jobs. The solution proposed for this scenario is to add surfactant or surfactant-based chemical additives at low concentrations to the cement slurry. The addition of surfactant to cement slurries has been proven to reduce rheological incompatibility between the slurry and SBM and the impact of contamination on set cement properties. This paper presents the laboratory test results, operational concerns, mitigation, and a case study showing the application and effectiveness of this technique comparing similar strings that were cemented in different wells.
Abstract Slag MTC is a unique cementing technique that drilling fluid is converted to cement slurry with the addition of blast furnace slag. By controlling slag activating speed and colloid content in MTC slurry, Slag MTC not only has the properties which meet the requirements of normal cementing jobs, but also shows the advantages slurry in rheology, transition time of static gel strength, settlement stability, volume shrinkage and compatibility with drilling fluid. After using slag MTC in 130 wells, we can say this technique not only can get good quality of cement job in normal wells but also is very useful for solving the problems of gas migration in high pressure well and poor quality in small clearance in directional wells and lost circulation in low pressure well. 100% of cement job were successful among these 130 wells. The authors described the advantages of this technique in solving cement problems of complex wells and analyzed the properties of slag MTC. Three cementing cases in typical wells are presented. Introduction MTC techniques have been studied for half a century, among which only slag MTC and Portland cement MTC make sense and have been used in drilling operations. Many cases show that slag MTC can not only improve the quality of cement job, but cut cementing cost. Cement engineers in China have concerned slag MTC since early 90's. Some research institutes and oil fields have set to study MTC techniques. So far, Studies on slag MTC have made good progress and this technique has achieved success in field application. Drilling Research Institute of CNSPC (China New Star Oil Company)has launched study on MTC since 1992 and already developed a whole set of techniques. Slag MTC has been successfully used in 130 wells in Chuanxi, Linpan, Huabei, Songnan, Subei and Tahe Oil fields. The achievements in slag MTC are listed as follows:Polymer mud, positive ion gel mud, brine mud and positive ion gel oil mud can be converted to slag MTC. The lowest mud weight is 1.03 kg/l and highest 1.92 kg/l. The shallowest well is 850m and deepest 3900m. Slag MTC has been used to cement surface, intermediate and production casing. Slag MTC slurry is pumped with normal cementing truck or on-site mud pump. Success rate of cement operations reaches 100%. The quality of cement meets the requirements of production and stimulation, e.g. fracturing operation. The earliest formed slag MTC cement around production casing has kept intact for 6-year production. Slag MTC cementing can cut cost by 5–38% compared with conventional cementing.
- North America > United States > Texas (0.28)
- Asia > China > Xinjiang Uyghur Autonomous Region (0.24)