No abstract

Hydraulic fracturing has been used for many years in order to stimulate the oil and gas wells for improving the reservoir production. Many investments are allocated for hydraulic fracturing all around the world to develop hydrocarbon resources. Most of them are done for cased holes which some of them do not significantly improve the hydrocarbon production. The main reason is improper fracture initiation and complex near-wellbore fracture geometry which is a challenging problem. In cased holes, the perforations are the only connection between the well and the reservoir, therefore the fracture initiates somewhere in the perforation. Understanding the stress distribution around the perforations is the key for analyzing the fracture initiation mechanism and thereby the near-wellbore fracture geometry. In this paper new analytical formulas are derived and applied along with numerical methods to simulate the stress profile around the perforations. Having analyzed the perforation stress distribution, it is possible to understand the mechanism of fracture initiation and consequently improving the near-wellbore fracture geometry. Results of this model are presented at some in-situ stress regimes, cement and rock properties, and also perforation and well parameters. It is concluded that, at any specific stress regime, there is an optimum well design and completion, and also perforation orientation, which leads to lower fracture initiation pressure as well as better fracture orientation geometry in terms of less near-wellbore fracture tortuosity. Therefore, better connection can be developed between the borehole and the reservoir formation. The importance of this model is its ability in analyzing the stress profile along the perforation tunnel, so more realistic fracture initiation pressure and fracture geometry can be estimated for better well completion and perforation design.

Ahwaz oilfield is one of the southern Iranian fields in the Middle East that are located in reverse fault stress regime. Wells A and B are two deviated wells with same drilling conditions that produce oil from Bangestan reservoir in Ahwaz oilfield. Numerous cases of borehole instability, stuck pipe, and borehole collapse have been reported while drilling well B. These problems cause highly increasing of drilling operation cost of well B. However, well A has been drilled without any serious problems. To investigate and avoid these problems and improving operating costs of drilling, a comprehensive mechanical stability analysis is essential. To do so, a computer program is developed to analyze the mechanical stability of these deviated wellbores. The mechanical stability analysis reveals that in the reverse fault stress regime, drilling in direction of maximum horizontal stress is the most stable direction. But drilling in direction of minimum horizontal stress, leads serious borehole instability and borehole collapse. Comparing the results with trajectory of two deviated wells, show that well A has been drilled in direction close to the maximum horizontal stress while well B has been drilled in direction of minimum horizontal stress. As result well A must be more stable than well B. Base on the results the best drilling direction in Ahwaz oilfield is parallel to maximum horizontal stress.

The present study investigates the aminothermal synthesis of SAPO-34 using various templates, including morpholine, diethylamine, triethylamine, triethanolamine, diglycolamine, and diisopropylamine, under static conditions. The catalyst's characteristics were assessed through XRD, SEM, and EDS analyses, and the catalytic behavior of the samples was studied in the MTO reaction. The results indicate that only morpholine leads to the formation of pure SAPO-34, and it is essential to regulate the crystallization time to prevent the formation of SAPO-20. Furthermore, the impact of the order of reactant addition and the intensity of stirring during aging on catalyst characteristics was investigated, and the outcomes were compared to those of the hydrothermally synthesized sample. The findings reveal that the aminothermal method reduces the crystallization time and enhances silica incorporation. However, this technique is recommended for the synthesis using polar templates or in the presence of polar additives. The utilization of non-polar templates such as DEA and TEA resulted in very thick pastes. The catalytic performance of the aminothermal samples was comparable to that of the hydrothermal samples, with a methanol conversion of over 98% and a selectivity to light olefins of approximately 80%. Nevertheless, the impact of preparation, aging, and post-treatment conditions on the hydrogen transfer index and alkanes production was significant.