Well construction is one of the greenhouse gas (GHG) emissions contributors in the oil and gas industry. Today, the main attention is paid to technology solutions, minimizing drilling time and rig upgrading with low-energy equipment. However, what about optimum well design itself, which may lead to acceptable operational risks, reasonable budget, lower power demand and consequently lower emissions to deliver it?The work presented in this paper is about the planning process to reach not just a technical and financial balance in the construction of a well, but also incorporate sustainability elements into the design process itself.

The conventional engineering approach to designing a well, namely being able to meet its technical targets within reasonable budget, was upgraded with an additional workflow to consider the GHG emission footprint of well construction process. Specifically, it was incorporated in a digital solution which enables a comparison between different well program scenarios, from which an optimal design can be chosen. The process includes the following step: 1) creation of a well design meeting its technical targets; 2) estimation of the well budget; 3) modeling the well construction GHG emissions for the different designs. Some iterations of this process are needed to reach sustainable well design (relatively optimal case).

The real extended reach drilling (ERD) well proposal was used as the example for this study. The3D geomechanical model was created prior to start the well engineering. It simulated distribution of stresses which enabled calculation of the safe pressure window while drilling, tripping, running casing and cementing. Considering this model, the originally proposed casing design was upscaled to achieve the ECD (Equivalent Circulating Density) in the required range without collapsing and breaking down the wellbore wall. Additionally, the trajectory was optimized to improve hole cleaning and facilitate the running of casing in highly deviated sections of the well. All these measures theoretically minimized the risk of not hitting the planned targets. Then, the well profile was tuned to improve the financial impact and operational emission footprint without compromising technical solution. As a result, it had led to potential lowering of the well construction budget by ~2 % and reduction of the emission by 6.3 % (for the sum of Scope 1and 3 emissions).

The main idea of this approach is to achieve a low-energy, cost-effective and technically feasible well design as a baseline. Within the constraints of this design, it will then leverage specific technology solutions to further minimize energy consumption and GHG emissions.

This manuscript presents a new methodology for the engineering design process for oil and gas wells, which quantitively incorporates sustainability. The ideas, which are expressed in the manuscript, can be implemented in any drilling project worldwide.