## 3 Exploration and Production
### Well Types and Fracturing Fluids  
In addition, horizontal well drilling has been used extensively in shale oil and gas reservoirs. Shell applied horizontal drilling technology for developing oil shale resources in Colorado's Picance Basin Shell demonstrated and commercialized shale oil recovery via a second-generation ICP (in situ conversion process) with the assistance of horizontal wells. The ICP involves leaching saline minerals with hot water to develop permeability first. Lab pyrolysis experiments and reservoir simulation studies were completed alongside with baseline hydrological monitoring program in place.  
[PERSON] et al., proposed a novel method for oil shale in situ conversion using multilateral wells, which improve heat transfer and production rate in thin oil shale formations by increasing contact with the reservoir. A 3D transient model is developed to analyze the temperature field, chemical processes, production data, and energy performance. Sensitivity analyses of oil shale properties, injection management, and multilateral well structures are conducted, revealing the strong dependency of hydrocarbon yield on oil shale temperature and the sensitivity of production time to specific heat capacity, injection fluid temperature, and mass flow rate. The research suggests that optimal performance can be achieved with 5-branch wells, 60-degree branch angles, and 40 m branch lengths. The study provides valuable insights and recommendations for improving oil shale recovery and utilization through the application of multilateral wells in in situ conversion processes [51].  
[PERSON] et al., conducted numerical simulations of kerogen pyrolysis by the in situ upgrading process of Steamfrac, which entails the steam or hot-water injection into multistage transverse fractured horizontal well systems. The study analyzed the sensitivity of the temperature distribution of the reservoir to the positions of horizontal wells and productivity by applying two different irreducible saturation of the aqueous phase in the rock matrix. The research shows that recovery and utilization of oil shale could be improved through the use of multistage transverse fractured horizontal well systems [52].  
[PERSON] et al. (2017) combined the fracturing fluid with iron oxide nanoparticles, which is used to facilitate the extraction of oil from oil shale. This process integrates microwave technology and hydraulic fracturing, wherein the hydraulic fracturing fluid enhances permeation channels in the shale matrix, ensuring effective oil production [53].  
Microwave irradiation is used for the thermal decomposition of kerogen, the main organic component in oil shale, into oil. The iron oxide nanoparticles act as microwave absorbers, converting the microwave irradiation to energy, thus enabling the high temperatures necessary for the transformation of oil shale. Oil extraction offers several benefits over traditional methods. Compared to conventional heating, microwave irradiation results in a faster process, lower energy usage, and increased oil production. Additionally, the quality of the extracted oil is improved, with the method both breaking down the chemical bonds in larger molecules to convert them into lighter hydrocarbons and reducing the contents of nitrogen and sulfur. As a result, the oil is potentially upgraded into petrochemical products with high saturation and aromatic compositions. The most effective results, in terms of yield and quality of oil, were found in the sample group exposed to a microwave output power of 800 W, a reaction temperature of 950 \({}^{\circ}\)C, and 0.1 wt% iron oxide nanoparticles. However, this method's efficiency is still subject to further investigation and potential technological advancements, particularly in material technology, to withstand higher in situ reaction temperatures.