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Lost circulation (LC) is commonly encountered in drilling and cementing operations and can be a costly problem that increases nonproductive time (NPT). Various methods can be applied to control losses—from applying best operational practices to incorporating LC control materials in treatment fluids and cement slurries. Among the cementing challenges, the loss of circulation can also be associated with poor zonal isolation and becomes more critical when zones between reservoirs should be covered to avoid sustained casing pressure (SCP) in the future and to extend the life of the well. The application for this tailored spacer was the first one globally. Challenges addressed in the largest offshore field loss zone in the UAE included a high likelihood for losses during initial cementing, narrow equivalent circulating density (ECD) gradient, uncertainty in bringing cement to surface in the casing operation, and zonal isolation between reservoirs, formation, and caprock. As part of the best cementing practices, the design and tailoring of the spacers should be considered. Correct use allows the cement to cover zones of interest with less contamination, and cement properties can develop and interact efficiently with the formation. Using a tailored spacer fluid system engineered to effectively and efficiently help prevent LC and maintain wellbore stability while preparing the wellbore to receive cement is discussed. The tailored spacer system uses additive synergies to help prevent LC in porous and fractured formations and enables control of rheological hierarchy and wellbore fluid displacement efficiency. The spacer was designed to optimize cementing operations where losses are observed and, in this case, incorporate additional LC materials to help prevent severe losses and achieve the desired top of cement (TOC). The tailored spacer system was pumped ahead of the cement slurry, to reduce permeability across the formation, with superior properties that help prevent fluid loss of the cement to the permeable formations. Enhancing the cement bond and allowing an effective mud removal differentiate it from a conventional spacer. Using this spacer system enabled cementing goals to be achieved. Cement was brought to the surface, casedhole logs exhibited excellent cement bonding, and no SCP was registered, helping eliminate the need for unwanted remedial operations to secure the zonal isolation, which saves rig time.

Cementing operations seek to minimize non-productive time (NPT) as part of the broad effort to optimize costs. A commonly encountered event that contributes to NPT is lost circulation. Lost circulation may often be associated, and treated, during drilling operations, but can occur during cementing practices, e.g. while running casing in the wellbore and/or circulating cement and treatment fluids. When fluids are lost to the formation and not appropriately cured, cementing objectives may not be met and, ultimately, zonal isolation can be compromised. Additional costs may be incurred to remediate the well construction and achieve a dependable barrier. It is, therefore, of great interest to develop and implement solutions which can facilitate the prevention and treatment of lost circulation. Described herein is the evaluation and use of a new tailored spacer system (TSS) engineered to effectively prevent lost circulation and maintain wellbore stability. The TSS was designed for use in cementing shallow water Caspian Sea wells with permeable formations and a history of losses. The spacer was subjected to conventional spacer tests and simulations including rheological measurements, compatibility assessments and fluid modeling to ensure job requirements would be met. Loss control tests were performed to verify the efficacy of the TSS to effectively prevent losses. All screenings demonstrated the TSS would be well-suited for the intended field application. The spacer system was successfully deployed in Caspian Sea wells and helped meet cementing objectives where conventional treatments failed.

In certain regions of oil and gas operations, lost circulation is a common occurrence, especially when a majority of the openhole exposed during primary cementing is carbonate-based formations. This can lead to lost circulation risks in most applications. To overcome lost circulation risks during primary cementing, a new tailored spacer system shows to improve the cement placement success. The manuscript discusses the quality assurance and performance testing with field cases demonstrating the value contributions of the spacer for achieving zonal isolation requirements as well as the top of cement objectives. The work efforts presented shows a spacer meeting and sometimes showing incremental wellbore strengthening in comparison to the published literature for existing available spacers used to overcome similar lost circulation risks.

Lost circulation (LC), commonly encountered in drilling and cementing operations, can be a costly problem that increases non-productive time, especially in highly permeable formations. When LC occurs during cementing, zonal isolation can be compromised. Risks associated with LC affect most applications, including offshore operations. This paper presents the evaluation of a new tailored spacer system (TSS) designed to effectively mitigate LC and its use in deepwater cementing operations to meet zonal isolation objectives.

Drilling and cementing operations commonly experience lost circulation (LC), which can result in non-productive time (NPT) and excessive costs. Losses were encountered while performing an offshore workover well operation in the UAE that challenged isolation objectives involving spotting a cement plug through coiled tubing. Selection of lost circulation treatments that may be deployed through coiled tubing is limited, increasing the difficulty in addressing losses. Previous attempts to cure losses and spot the cement plug were unsuccessful. This paper describes the application of a new tailored spacer system (TSS), engineered to reduce formation permeability and prevent lost circulation. Placement occurred through coiled tubing to successfully control losses in the thief zone, enable tagging of cement plugs, and achieve isolation for the zone of interest. The new TSS has been used on multiple cementing operations to mitigate losses, improve circulation, achieve top of cement (TOC) objectives, and eliminate remedial work; however, this case is the first global application of the TSS through coiled tubing in a plugging operation to stop lost circulation. Correctly evaluating and interpreting the well conditions, risk identification, analysis, and communication amongst operations personnel, and execution of good cementing operational practices led to utilization of the new TSS for this specific scenario of placement through the coiled tubing ahead of the cement slurry. Losses were prevented leading to a successful plug operation and enabling cementing goals to be achieved.

Lost circulation (LC) is commonly encountered in drilling and cementing operations and can significantly contribute to non-productive time (NPT). An operator in the Kyumbinskoe Field faced this challenge in a fractured production section of the formation, and conventional LC solutions had been ineffective at achieving strict regulatory top of cement (TOC) requirements and satisfactory cement bonding. This paper describes a tailored spacer fluid system engineered to effectively and efficiently prevent LC to meet the job requirements. The tailored spacer system includes additives that perform synergistically to help prevent LC in permeable and fractured formations and enables rheological hierarchy to facilitate effective mud displacement. The spacer was designed to meet operational parameters for cementing a production casing string in two stages through the use of a multi-stage tool and was subjected to thorough verification through lab testing and computer simulations to ensure job requirements could be met. The tailored spacer system was used in three trial jobs to assess its ability to minimize losses in a permeable and fractured formation with a history of LC with the ultimate goal to achieve planned TOC and improve cement bond quality as verified by Cement Bond Logs (CBL’s). Use of this tailored spacer system helped to minimize losses experienced on all three wells. CBL results were also significantly improved with an average of 70% of the cemented interval being classified as "good bond" on wells cemented without the tailored spacer system to 88% on the three wells where it was used. Barrier dependability with the new spacer system was improved through achieving strict regulatory requirements for TOC on two out of three wells and improved cement evaluation results, which is a critical requirement of well construction that allows for maximizing production over the life of the well.

Offshore cementing operations may require the use of liquid additives for logistical and blending requirements. Some additives should be suspended in hydrocarbon fluid because the active material cannot be readily liquefied in water. These suspensions often exhibit rheological instability and high viscosity, posing issues with shelf life and dosing through delivery lines. This paper describes the use of an innovative liquid cement additive designed to overcome limitations of conventional oil-based suspensions and improve cementing operations. The new microemulsion fluid loss additive overcomes shelf-life stability and fluid transfer issues inherent to conventional oil-based suspension additives, while providing excellent fluid loss control in cement. Shelf-life stability and fluid transfer rates affect the quality of mixing cement slurry, reduce delivery/pump rates, and extend overall job times. The microemulsion fluid loss additive chemistry was verified to provide improved shelf-life stability and reduced viscosity. Fluid loss, mixability/rheology, and stability tests in cement slurry evaluated the additive performance. Flow tests and calibrations using conventional liquid additive injection pumps were performed before deployment. Benefits of the microemulsion fluid loss additive were validated in a cement design for deepwater offshore work.

Amorphous Ru(P) films grown by chemical vapor deposition at 575 K using a single source precursor, cis-RuH2(P(CH3)3)4, or dual sources, Ru3(CO)12 and P(CH3)3 or P(C6H5)3, are studied. The phosphorus percentage affects the film microstructure, and incorporating >13% P resulted in amorphous Ru(P) films. While codosing P(CH3)3 with Ru3(CO)12 improves film step coverage, the most conformal Ru(P) film is obtained with cis-RuH2(P(CH3)3)4. A fully continuous 5 nm Ru(P) film is formed within 1 μm deep, 8:1 aspect ratio trenches. The barrier performance is tested using Cu/Ru/Si(100) stacks annealed at 575 K, and sheet resistance was used as a measure of barrier failure. Cu diffusivity in physical vapor deposition (PVD) Ru is approximated to be 6.6×10−17 cm2/s at 575 K, which indicates fast Cu diffusion along the grain boundaries. While 26 nm polycrystalline PVD Ru failed after 6 h annealing by Cu penetration, 28 nm amorphous Ru(P) survived after 67 h annealing. First principles density functional calculations sugg...

Reaction of 3,5-(CF3)2PzLi with [Cp*RuCl2]n (2:1) in diethyl ether at −78 °C gives [(Cp*RuLi)2(μ4-O)(μ2-Cl)(μ-3,5-(CF3)2Pz)3] (1) in 75% yield [3,5-(CF3)2Pz = 3,5-bis(trifluoromethyl)pyrazolate]. With a 1:1 ratio of [Cp*RuCl2]n to 3,5-(CF3)2PzLi, dark-green crystalline [Cp*Ru(μ-Cl)]2(μ-3,5-(CF3)2Pz) (2) is produced in ca. 50% yield. The reaction of 3,5-(CF3)2PzLi with [RuCl2(1,4-Me,iPrC6H4)]2 in diethyl ether at −78 °C gives the chloride-bridged dimer [RuCl(η6-1,4-Me,iPrC6H4)(μ-3,5-(CF3)2Pz)]2 (3) in 65% yield. The reaction of Cp*Ru(OSO2CF3)2 with 3,5-(CF3)2PzLi (2:1) in diethyl ether at −78 °C produced the unusual dinuclear RuIII−RuIII complex [Cp*Ru(μ-O)(μ-η5,η1-C5Me4CH2)Ru(η1-3,5-(CF3)2Pz)]·0.25Et2O (4) in 75% yield. Complexes 1–4 have been characterized spectroscopically and by single-crystal X-ray diffraction studies.

Chemical vapor deposition growth of amorphous ruthenium–phosphorus films on SiO 2 containing ∼ 15% phosphorus is reported. cis -Ruthenium(II)dihydridotetrakis-(trimethylphosphine), cis -RuH 2 (PMe 3 ) 4 (Me = CH 3 ) was used at growth temperatures ranging from 525 to 575 K. Both Ru and P are zero-valent. The films are metastable, becoming increasingly more polycrystalline upon annealing to 775 and 975 K. Surface studies illustrate that demethylation is quite efficient near 560 K. Precursor adsorption at 135 K or 210 K and heating reveal the precursor undergoes a complex decomposition process in which the hydride and trimethylphosphine ligands are lost at temperatures as low at 280 K. Phosphorus and its manner of incorporation appear responsible for the amorphous-like character. Molecular dynamics simulations are presented to suggest the local structure in the films and the causes for phosphorus stabilizing the amorphous phase.

The utilization of enones as latent enolates enables regioselective enolate formation from chemically robust presursors. In this communication, we report a catalytic Michael cycloisomerization of bis(enones) under Morita−Baylis−Hillman conditions. Upon exposure to 10 mol % tributylphosphine, bis(enone) substrates afford both five- and six-membered ring products. Notably, unsymmetrical bis(enones) possessing sufficient steric or electronic bias yield single isomeric products.

Reactions of the "salen" type Schiff bases H(2)L(1) and H(2)L(2) with Cd(OAc)(2).2H(2)O gave complexes with Cd(2) and Cd(3) cores and an extended 1-D framework architecture [H(2)L(1) = N,N'-(1,2-phenylenyl)-bis(5-bromo-2-hydroxy-3-methoxybenzaldimine; H(2)L(2) = N,N'-(propyl)-bis(5-bromo-2-hydroxy-3-methoxybenzaldimine)].

Triruthenium dodecarbonyl and trimethylphosphine or triphenylphosphine, and cis-ruthenium(II)dihydridotetrakis-(trimethylphophine) were used in flowing hydrogen or argon at 575 K to explore the effect of changing the percentage of P on the amorphous character of the films and on the electrical properties of the films. First-principles density-functional calculations are presented that reveal the interaction of Ru with P, and that predict the amorphous structure should be most stable above 20 at.% P and 10 at.% B. The films contained a carbon impurity that depended on the delivery gas and the alkylphoshphine source; film resistivity was highly dependent on the carbon impurity level. The microstructure changed with the percentage P; amorphous films formed provided the percentage of P exceeded 15 at.%. Film resistivity was most sensitive to the carbon impurity and also changed with microstructure. A 15 nm thick, amorphous film containing ∼15 at.% P had a resistivity of 210 μohm-cm.

[reaction: see text] Thioenoates are found to participate in highly chemoselective catalytic crossed Michael cycloisomerization with appendant aryl ketone and enoate partners to afford cyclopentene and cyclohexene products. This methodology has enabled a concise total synthesis of the potent molluscicide (+/-)-ricciocarpin A.

Electropolymerization of bithiophene-substituted cadmium(II) Schiff base complexes forms thin conducting metallopolymer films with metal centers distributed throughout. The metal centers act as seed points for direct growth of CdS nanoparticles within the polymer matrix under mild reaction conditions. This synthetic approach offers control over both the size and distribution density of the nanoparticles formed within the polymer film. The resulting hybrid materials hold promise for a variety of organic electronic and optoelectronic applications.

Thin films ( approximately 30 nm) of amorphous RuP alloys (P approximately 15-20%) can be grown by CVD from the single source precursor cis-H2Ru(PMe3)4 at 250-300 degrees C and 200 mTorr pressure on native SiO2.

Exposure of enone substrates 1a-18a, which possess appendant ketone, ester, and nitrile moieties, to Et2Zn in the presence of catalytic Cu(OTf)2/P(OEt)3 provides the cyclized products in good to excellent yields and diastereoselectivities. These results represent the first use of ketones, esters, and nitriles as terminal electrophiles in Cu-catalyzed conjugate addition-electrophilic trapping.

The utilization of enones as latent enolates enables regioselective enolate formation from chemically robust presursors. In this communication, we report a catalytic Michael cycloisomerization of bis(enones) under Morita-Baylis-Hillman conditions. Upon exposure to 10 mol % tributylphosphine, bis(enone) substrates afford both five- and six-membered ring products. Notably, unsymmetrical bis(enones) possessing sufficient steric or electronic bias yield single isomeric products.