Research and Application of Micro-Expansion and Anti-Channeling Cement Slurry System in Agadem Oilfield

The overall liner cementing qualification rate is only 40% in Agadem block of Niger, The cement slurry system used in the field has a UCA transition time of 43min, and an expansion rate of -0.03% in 24h, which result in a poor anti-gas channeling performance. The expansive agent and the anti-gas channeling toughening agent of anti-channeling agent were optimized through experiment study. A novel micro-expansion anti-gas channel cement slurry system which is suitable for Agadem block was obtained through experiment optimization study: 100% G +2 ∼ 4% fluid loss agent +3 ∼ 4.5% anti-channeling agent +1 ∼ 2% expansion agent-100S +0.15 ∼ 0.4% retarder +0 ∼ 0.3% dispersant +0 ∼ 0.25% defoamer + water. This new cement system has a good anti-gas channeling performance, the cement strength is 24.5-35.0MPa after 24hrs, the UCA transition time is 16-18min, and the expansion rate is 1.5-1.7%. At the same time, a cementing prepad fluid suitable for the block and the micro-expansion cement slurry system is selected to ensure the performance of the cement slurry's anti-channeling performance. The field test results proofs the good performance of the new cement system. The cementing qualification rate of Koulele W-5 well is 96%, and the second interface cementation is Good. The cementing qualification rate of Trakes CN-1 well is 100% which second interface cementation is Excellent. This paper has positive guidance and reference for cementing in Agadem block.

Experimental Study on Gangue Backfilling Materials Improved by Soda Residue and Field Measurement of Surface Subsidence

In coal mining, the problems of massive discharge of solid waste, environmental pollution, and surface subsidence disaster are urgent to be solved. Based on this engineering background, the feasibility of using solid waste soda residue to improve gangue cemented backfilling material was discussed, and the surface subsidence of the test working face was measured in this study. Besides, the influence of soda residue on the performance of gangue cemented backfilling materials was analyzed through laboratory tests. The experimental results show that 1) as the content of soda residue increases within the range of 0–12%, the slump of the soda residue gangue backfilling material (SRGBM) slurry gradually increases, and the bleeding rate increases. The early strength and later strength of SRGBM increase first and then decrease with the increase in soda residue content. 2) The optimal ratio of the soda residue cemented backfilling material is soda residue: fly ash: lime: cement: gangue = 6%: 34%: 10%: 2.5%: 47.5%. Compared with the reference group, the slump of the material is increased by 12.7%, the bleeding rate is only 3.8%, and the early strength and later strength are increased by 449 and 187%, respectively. 3) The addition of soda residue promotes the hydration reaction of the slurry system of soda residue cemented materials. The coexistence of C-S-H gel and N-A-S-H gel reduces the connectivity of pores and improves the strength of the material. 4) The maximum surface subsidence of the test working face is only 245 mm, and the surface subsidence control effect is good. Therefore, the preparation of SRGBM with soda residue can achieve energy saving and emission reduction, with significant technical, economic, and social benefits, and has good promotion and application value.

Design and Evaluation of High-Temperature Well Cementing Slurry System Based on Fractal Theory

The efficient development of oil and gas resources is inseparable from the progress of drilling technology and the safety of the long life cycle of wellbore. At present, exploration and development is expanding to deep and ultra-deep areas. The long life cycle safety of deep and ultra-deep wells is mainly realized by the sealing performance of cement slurry. Additionally, the accumulation degree of cement slurry particles is closely related to sealing performance. Based on fractal theory, an accumulation model of continuous distribution of additive material particles was designed, which can determine the range of fractal dimension necessary to realize the tight stacking and guide the proportion of solid admixture. The formulation of high temperature-resistant cement slurry was prepared by designing the ratio of solid admixture and optimizing the high temperature-resistant liquid admixture. The evaluation of engineering and temperature resistance of the cement slurry proves the rationality of the accumulation model, which can be applied to the design of a high temperature cementing slurry system in deep and ultra-deep wells.

Unconventional Single Slurry Solution for ERD Wells with Depleted Formations

Tailoring slurry designs using amorphous liquid silica base has been a success for Cementing Extended Reach Drilling (ERD) wells in Brunei in development fields. The use of this unconventional slurry density and design has helped to achieve the necessary top of cement and required zonal isolation for the production string of these wells. Cementing across depleted formations has been a challenge for the drilling sector within the oil industry. Isolation of production zones with competent cement slurries has become a necessity in fields, especially where a low Equivalent Circulating Density(ECD) during the cementing operation is required to achieve the desired top of cement in low fracture gradient formations. For Brunei offshore operations a novel approach has been proposed that uses an amorphous liquid silica-based slurry system to design a new 14 ppg lightweight cement slurry. The slurry properties were tailored to eliminate the need for a dual slurry system. Planning, execution, and post-operation evaluation methods have been developed for this new design. Extensive laboratory testing has been performed for the 14 ppg extended slurry which includes basic slurry testing as well as more advanced evaluations such as a full mechanical properties study and finite element analysis that was used compared to conventional slurry designs. Various optimizations were done for the slurry design to overcome mixability challenges and deployment using a conventional offshore liquid injection system or by premixing the water with liquid additives on a mixing tank or rig pits. To validate this technology, a field trial was performed at the rig site where a production liner for an extended reach well was cemented and subsequently evaluated using cement evaluation logging tools. The first Brunei offshore trial operation, executed in Q2 2020, was a 4.5-in. production liner where 16.5 m3 of a 14ppg novel slurry design was mixed, pumped and successfully placed within the annulus. Since the initial trial, a total of 8 jobs have been executed successfully in Brunei, with a few more wells identified as candidates for this solution. The paper provides laboratory testing details, hydraulic simulation validations along with job execution and post-operation cement evaluation.

West Africa Salt-Zone Cementing Best Practices: Laboratory Evaluation and 5-Year Field Application Review

Summary To determine which salt-based cement system (potassium chloride or sodium chloride) was suitable for cementing across halite and anhydrite salt sections in West Africa, eight slurry recipes were tested to assess how formation salt contamination would affect slurry properties. The formation salt used for testing was sampled from a deepwater, presalt well in Angola. The recommendations developed from the laboratory study were implemented in 10 projects across West Africa over 5 years with 100% operational and well integrity success. A candidate deepwater well was selected in which the surface and intermediate strings penetrated salt formations. Four slurry designs (a lead and tail slurry used on each casing string) were programmed. Each slurry was designed and tested as two distinct systems using potassium chloride and sodium chloride salt, respectively, yielding a total of eight slurry designs. Using the methodology and data presented by Martins et al. (2002), the mass of dissolved formation salt that each slurry may receive during placement was estimated and duly incorporated into each slurry design. Subsequently, the salt-contaminated slurries were tested and compared with the properties of the initial uncontaminated slurries. On the basis of these results, conclusions were then made on which salt slurry system (potassium chloride or sodium chloride) exhibited better liquid and set properties after contamination with formation salt. Subsequently, this knowledge was applied to 10 projects across three countries in West Africa. This study showed that when the contact time of liquid cement slurry to salt formation was low—typically when the salt-formation interval across which the cement slurry flowed was less than 100 m thick—the level of formation salt dissolution entering the slurry during placement was limited. In this case, a potassium chloride salt-based slurry delivered improved liquid and set properties as compared with a sodium chloride salt-based slurry. In the field, this knowledge was applied in all oilfield projects cemented by an oilfield service company between 2015 and 2020. This included deepwater, shallow offshore, and onshore wells. All related salt-zone cement jobs, including sidetrack plugs, placed across the salt formations were successful on the first attempt. In an absence of industry consensus around salt-formation cement slurry design, this paper validates a guideline for West Africa, based on results from laboratory testing and 5 years of field application. In contrast to current literature that recommends only sodium chloride salt-based slurry designs across halite or anhydrite salt intervals, this work demonstrates that potassium chloride salt-based slurry systems can effectively be used to achieve well integrity where a halite or anhydrite salt interval is less than 100 m (328.1 ft) thick.

Laboratory construction of a novel elastic self-sealing cement slurry

The elastic self-sealing cement slurry is a novel slurry system, which is capable of facilitating self-repairs of cement sheath in the extreme wellbore conditions, but it involves seldom approached. In this work, a novel elastic self-sealing cement slurry is designed and preliminarily established, by means of screening the functional additives. The main compositions of elastic self-sealing cement slurry are determined, which will provide important information for the development of high performance self-sealing cement slurry systems.

Light-triggered hydrogen production from anhydrous alkaline methanol on a multi-layer device

Hydrogen production from methanol has attracted substantial interest because of the clean combustion of hydrogen and the convenience of methanol in storage and transportation. However, it requires high-temperature and high-pressure conditions to reform methanol with water to hydrogen with high turnover frequency (TOF, e.g. 104 moles of hydrogen per mole of Pt per hour). Here we show that hydrogen can be produced from anhydrous alkaline methanol with a remarkable TOF of 1.8×106 moles of hydrogen per mole of Pt per hour on a light-triggered multi-layer system under mild conditions. The performance is attributed to the use of anhydrous methanol as both the proton source and the hole scavenger in alkaline conditions. In contrast to a slurry system, we show that the proposed multi-layer system avoids particle aggregation, and it leads to the effective utilization of methanol, light and Pt active sites. This notable performance steps forward to the practical light-triggered hydrogen generation.

PSI-16 Investigation of Jute to Stimulate Sow Nesting Behavior in Farrowing Crates

Domesticated sows are highly motivated to perform nesting behavior prior to farrowing. However, due to the potential for clogging slurry systems, large amounts of nesting material are not practical to use in most production systems. Therefore, the study objective was to assess an alternative nesting material provided prior to farrowing on sow welfare and reproductive outcomes. We hypothesized that the provision of jute nesting material would decrease sow stress and improve reproductive outcomes. Twenty-one sows were randomly assigned to 1 of 2 treatments: farrowing crate with jute nesting material (n = 11; 40.64 x 21.59 cm) or farrowing crate without nesting material (n=10). Three overlapping jute pieces were attached to the front of the crate to prevent substrate from falling through the slatted floors and disrupting the slurry system. Sows had access to the jute from the time they were moved into the crates (112.4 ± 0.5 d of gestation) until the end of farrowing. Saliva samples were collected, as a non-invasive way to measure cortisol and immunoglobulin A (IgA) to assess stress, on d -1, 0, 1, and 2 relative to farrowing, and a final sample was collected at weaning. Video was continuously coded for observations of jute-oriented interactions. Data were analyzed as GLM using JMP. In the 12 h prior to farrowing, sows spent an average of 30.02 ± 33.12 min interacting with the jute. Although the sows appear to interact with the material, farrowing duration, number of stillborns, IgA, and cortisol did not differ between treatments (P > 0.05). In summary, the treatment was likely not robust enough to satiate the sows’ nest-building needs. Therefore, alternative nesting materials that provide a better outlet for sow behavior, while avoiding negative effects on the slurry system, or ways to present that material should be evaluated to improve sow welfare.