Comparative Study on Calculation Methods of Mud-Weight Window for Subsalt Wells: 1-D, 3-D, and Integrated 3-D Methods

Abstract

Owing to the complex distribution of stress directions around a salt body, accurate prediction of mud-weight window (MWW) for subsalt wells has presented a challenge to the industry for a long time. This paper presents a comparative study on methods practically used in calculating the mud-weight window of subsalt wells. Selected methods, which include the 1-D analytical method, 3-D numerical method, and the integrated 3-D method, are compared. A subsalt well section in deepwater GoM was chosen as a validation example. Both workflows of each calculation method and resultant MWWs obtained with each method are analyzed and compared. The TVD depth of the investigated subsalt well section is from 22,000 to 30,000 ft. The salt body's thickness along the wellbore trajectory is 20,000 ft, and its width is 18,000 ft. With seismic sectional data, an anti-cline structure is constructed accordingly at its bottom surface. Mohr-Coulomb criterion is adopted in the calculation of MWW. A 1-D solution of MWW is calculated with the geostress field derived from overburden stress along the trajectory. A 3-D solution of MWW is calculated with the stress values obtained with finite-element submodeling techniques. An integrated 3-D solution of MWW is calculated with the 3-D stress field obtained from the finite-element method and an analytical tool for MWW calculation along the trajectory without using the submodeling technique. Comparisons have been made between the results obtained with the conventional 1-D method, 3-D finite-element submodeling method, and the integrated 3-D method. Solutions obtained with the conventional 1-D method have missed the abnormality of stress distribution at the salt base and have smaller values of MWW compared to the other solutions. The solution of MWW obtained with the integrated 3-D method is very close to the one obtained with the finite-element submodeling method, but at only one-tenth of the time cost. With the validation example of the subsalt well section, a comparison of workflows and the resultant MWW's accuracy has illustrated the advantages and disadvantages of typical 1-D, 3-D, and integrated 3-D method for MWW calculation. The results presented in this paper can be used as a reference deciding on the best practice for calculating the MWW of subsalt wells. This work also presents an example of best practice.

Positron Emission Tomography-Guided Photodynamic Therapy with Biodegradable Mesoporous Silica Nanoparticles for Personalized Cancer Immunotherapy

“…The schematic for PET-guided PDT-immunotherapy combination using a bMSN platform is shown in Figure 1. Briefly, bMSNs were synthesized using a heterogeneous oil-water biphase reaction system, 34 and the resulting bMSNs were surface-modified with (3aminopropyl)triethoxysilane (APS) to introduce amine groups. CpG and Ce6 were then loaded into mesopores of bMSNs via electrostatic and hydrophobic interactions, respectively.…”

“…Compared with the average pore size of 2.0-4.0 nm for conventional MSNs in the literature 29,30,37 and those from commercial sources, bMSNs with the unique 3D dendritic and hierarchical nanostructures have a higher average pore size, pore volume, and surface area (Figure S1a,b), thus potentially allowing a high loading capacity of macromolecular drugs, such as proteins and peptides. 34 Conventional MSNs are reported to undergo slow degradation over several weeks. 35 As our bMSNs were highly porous compared with conventional MSNs, we sought to investigate the degradation kinetics of bMSNs.…”

“…We speculate that the highly porous core of bMSNs with a less dense and low cross-linking Si-O-Si matrix allows for this rapid degradation. 34 Drug Loading, Release, and in Vitro PDT by bMSN Nanoplatforms.…”

“…[31][32][33] In addition, conventional MSNs could cause chronic tissue damage due to slow biodegradation and long-term retention in major organs. 34,35 To address these issues, we have developed small MSNs (~80 nm in diameter) with large 5-10 nm pore size and fast biodegradation rate as a multifunctional nanoplatform for combination immunotherapy (Figure 1). We coloaded these biodegradable MSNs (bMSNs) with CpG oligodeoxynucleotide (CpG ODN, a potent Toll-like receptor-9 agonist) and photosensitizer chlorin e6 (Ce6) for combination PDT-immunotherapy.…”

Chemical Engineering of Cell Therapy for Heart Diseases

“…Thus, we chemically engineered platelets with CD34 antibodies to find CD34-positive cells and transport them to the infarct site. 38 While this therapy paradigm still requires the isolation of platelets and their modification in vivo, it is simpler than large-scale cell manufacturing. Alternatively, it is feasible to create bispecific antibodies (BsAb) that possess an anti-CD41 and an anti-CD34 binding arm to capture both endogenous stem cells and platelets in vivo.…”