The Role of Filippi’s Glands in the Silk Moths Cocoon Construction

Filippi’s glands (FGs), formerly also called Lyonet’s glands, are accessory secretory structures of the labial (silk) glands of lepidopteran caterpillars, which were implicated to play an important role in the maturation of the silk material and the construction of the cocoon. In our previous study, we have identified several species of giant silk moths that completely lack the FGs. Interestingly, the absence of FGs in these species correlates with the construction of a loose cocoon architecture. We investigated the functions of FGs by their surgical extirpation in the last instar larvae of the silkworm, Bombyx mori. We found that the absence of FGs altered the structure of the resulting cocoon, in which the different layers of silk were separated. In further experiments, we found no effects of the absence of FGs on larval cocoon formation behavior or on changes in cocoon mass or lipid content. Differential proteomic analysis revealed no significant contribution of structural proteins from FGs to silk cocoon material, but we identified several low abundance proteins that may play a role in posttranslational modifications of some silk proteins. Proteomic analysis also revealed a difference in phosphorylation of the N-terminal sequence of fibroin-heavy chain molecule. Thus, FGs appear to affect silk stickiness during spinning by regulating posttranslational modifications. This could also explain the link that exists between the absence of these glands and the formation of loose cocoons in some giant silk moth species.

Crack formation behavior of composite fly ash – bentonite (FAB) in landfill liner system

This study aims to investigate the influence of different mixtures on the phenomenon of desiccation cracking in bentonite-fly ash mixtures as a landfill liner system. Fly ash is quite potential to be used as a landfill liner mixture because it has a low hydraulic permeability or conductivity value. This study uses class F fly ash from the Paiton power plant production process, Indonesia, which has been distributed commercially. Desiccation test was conducted in this study. The composition of fly ash and bentonite which is used are pure fly ash (FAB0), fly ash and bentonite 15% (FAB15), fly ash and bentonite 20% (FAB20) and fly ash and bentonite 25% (FAB25). The smallest CIF value is found in the pure fly ash layer. However, the pure fly ash cannot be used as landfill liner because the high permeability value. Therefore, the addition of bentonite will increase the possibility of crack formation. This study reveals that the addition bentonite in the fly ash composite will increase the crack. However, determining appropriate mixture composition is critical when working on the landfill liner system.

Identifying Formation Creep: Ultrasonic Bond Logging Field Examples

Summary As part of plug and abandonment (P&A) operations, several acceptance criteria need to be considered by operators to qualify barrier elements. In casing annuli, highly bonded material is occasionally found far above the theoretical top of cement. This paper aims to describe how the highly bonded material can be identified using a combination of ultrasonic logging data, validated with measurements in laboratory experiments using reference cells and how this, in combination with data from the well construction records, can contribute to lowering the costly toll of P&A operations. Ultrasonic and sonic log data were acquired in several wells to assess the bond quality behind multiple casing sizes in an abandonment campaign. Data obtained from pulse-echo and flexural sensors were interactively analyzed with a crossplotting technique to distinguish gas, liquid, barite, cement, and formation in the annular space. Within the methodology used, historical data on each well were considered as an integral part of the analysis. During the original well construction, either water-based mud (WBM) or synthetic oil-based mud (OBM) was used for drilling and cementing operations, and some formation intervals consistently showed high bonding signatures under specific conditions, giving clear evidence of formation creep. Log data from multiple wells confirm that formation behavior is influenced by the type of mud used during well construction. The log data provided information of annulus material with a detailed map of the axial and azimuthal variations of the annulus contents. In some cases, log response showed a clear indication of formation creep, evidenced by a high bond quality around the production casing where cement cannot be present. Based on observations from multiple fields in the Norwegian continental shelf, a crossplot workflow has been designed to distinguish formation from cement as the potential barrier element. NORSOK Standard D-010 (2013) has initial verification acceptance criteria both for annulus cement and creeping formation as a well barrier element, both involving bond logs; however, in the case of creeping formation, it is more stringent stating that “two independent logging measurements/tools shall be applied.” This paper aims to demonstrate how this can be done with confidence using ultrasonic and sonic log data, validated against reference barrier cells (Govil et al. 2020). Logging responses like those gathered during full-scale experiments of reference barrier cells with known defects were observed in multiple wells in the field. Understanding the phenomenon of formation creep and its associated casing bond signature could have a massive impact on P&A operations. With a successful qualification of formation as an annulus barrier, significant cost and time savings can be achieved.

The Mechanical Stratigraphy of Kerendan Field in Upper Kutai Basin: Implication to Field Development with Massive Carbonate Tight Gas Reservoir

Understanding of field mechanical stratigraphy in terms of formation behavior due to coupled interaction between formation pressure depletion and state of stresses is crucial to achieving successful field development. These provide technical advantages of having a solid foundation for implementation in advanced well construction and completion strategy, especially in light of emerging and challenging plays related to unconventional reservoirs. This paper describes full-field interaction between formation behavior in 4D Geomechanical analysis of Kerendan Field located in Upper Kutai Basin, Central Kalimantan area on gas-condensate production from massive carbonate tight gas reservoir. Integrated 1D/3D/4D geomechanics study workflow result has enabled characterization of each mechanical stratigraphy unit, as follows: The overburden section is comprised of Miocene deltaic clastic succession which is characterized as “soft formation” with low stiffness (Static Young’s Modulus of 0.5 to 1.8 Mpsi) and low - medium rock strength (UCS of 800 to 2000 psi); Reservoir section comprised of Oligocene tight carbonates platform which characterized as “hard formation” with medium stiffness (Static Young’s Modulus of 3.0 to 4.5 Mpsi) and medium rock strength (UCS of 5000 to 6900 psi); Underburden section comprised of Eocene mixed-carbonate clastic succession and Pre-Tertiary metasediments which characterized as “very hard formation” with high stiffness (Static Young’s Modulus of 4.5 to 5.0 Mpsi) and medium rock strength (UCS of 6500 to 7900 psi). The Kerendan field would require implementation of special drilling and stimulation techniques in order to achieve optimum full field development potential owing to its reservoir characteristics. The field’s exhibit a large areal extent and massive tight limestone reservoir with relatively high Young’s Modulus, which is favorable for the utilization of extended reach drill (ERD) / horizontal wells followed with multi-stage acid fracturing stimulation. 3D/4D Geomechanical analysis is essential to assess the drillability and engineering limits of various development scenarios which will be strongly controlled by geomechanical fabric, pre-existing deformation/local discontinuities, prevailing principal stress tensor and stress changes during field production.