Saudi Arabia has embarked on an exploration journey for its unconventional gas resources by recently targeting three different areas across the Kingdom. The targeted formations include tight sandstone, shale and tight carbonate with a permeability range of 200 nano-darcy to 0.1 MD. Extensive exploratory work has been performed in each of the areas through drilling vertical wells to identify and characterize potential targets through coring and open-hole logging along with flow potential testing of those targets after placing vertical fractures, which is beyond the scope of this paper. This paper highlights the progress of the unconventional program through drilling horizontal mono-bore wells and stimulating them with multistage fracturing using Plug-N-Perf technique. Three case studies, one from each targeted formations, are presented in this paper. The subjects addressed are: Well completion including the selection of tubing and liner sizes, metallurgy and grades along with performing stress and thermal analysis simulating the expected loads during proppant fracturing to determine the maximum safe loads at each stage. Proppant fracturing design including the number of stages and clusters, the spacing of stages, proppant type, size and volume, and fracturing fluid systems. The design is based upon the geomechanical and petrophysical interpretations of the openhole logs together with onsite calibrations and measurements. Plug-N-Perf and fracture stimulation operations and execution Fracture fluid clean up and flow testing The paper summarizes the workflow adopted, the lessons learned and challenges overcome after drilling, completing, fracturing and flow testing of several unconventional gas wells in Saudi Arabia.

Saudi Arabia has embarked on an exploration journey for its unconventional gas resources by recently targeting three different areas across the Kingdom. The targeted formations include tight sandstone, shale and tight carbonate with a permeability range of 200 nano-darcy to 0.1 MD. Extensive exploratory work has been performed in each of the areas through drilling vertical wells to identify and characterize potential targets through coring and open-hole logging along with flow potential testing of those targets after placing vertical fractures, which is beyond the scope of this paper. This paper highlights the progress of the unconventional program through drilling horizontal mono-bore wells and stimulating them with multistage fracturing using Plug-N-Perf technique. Three case studies, one from each targeted formations, are presented in this paper. The subjects addressed are:• Well completion including the selection of tubing and liner sizes, metallurgy and grades along with performing stress and thermal analysis simulating the expected loads during proppant fracturing to determine the maximum safe loads at each stage. • Proppant fracturing design including the number of stages and clusters, the spacing of stages, proppant type, size and volume, and fracturing fluid systems. The design is based upon the geomechanical and petrophysical interpretations of the openhole logs together with onsite calibrations and measurements. • Plug-N-Perf and fracture stimulation operations and execution • Fracture fluid clean up and flow testingThe paper summarizes the workflow adopted, the lessons learned and challenges overcome after drilling, completing, fracturing and flow testing of several unconventional gas wells in Saudi Arabia.

Gaining an understanding of the well to well interference during hydraulic fracturing and subsequently production interference is paramount in optimizing the costs associated with field development. Much work has been done in the industry to better understand the interference during hydraulic fracturing and production among adjacent wells. This paper presents an analysis that employed both a pressure interference analysis and chemical tracer analysis to gain a better understanding of the fracture interference in a well pad in the Jafurah field. The subject pad consists of 4 wells. Two of which run parallel in a north direction and the other two run parallel in the southern direction. All four wells were hydraulically fractured with slickwater design. Adjacent to the subject pad is another pad that had been previously stimulated with crosslink design and was used for pressure monitoring. The distance between the laterals was relatively similar (X ft) with one exception (2 × ft). Initially, one well from both directions was stimulated with 33 stages each of slickwater design and the plugs were subsequently milled out. Afterwards, the other two wells were stimulated with 33 stages of slickwater each. In 7 of the 33 stages of the later wells, 20 oil and 20 water tracers were injected in sequence in an attempt to study the physical extent of the fractures generated. While the latter two wells were being stimulated, the wellhead pressure on the parallel wells was being monitored and recorded along with the wellhead pressures on the adjacent pad. During flowback, the southern wells were flowed back simultaneously and flowback samples were collected to be analyzed for tracers. Subsequently, the northern wells were opened up to flowback in the same manner and flowback samples were also collected for tracer analysis. Wellhead pressure was monitored on the adjacent pad during flowback of all the wells. The pressure data during the fracturing operation indicated for distance × ft and the size of stimulation stages pumped, a level of communication which was further verified by the production interference analysis as well as the tracer data.

Unconventional resources in Saudi Arabia symbolize an opportunity to extend required gas plateaus in the long term, to substitute gas for liquid fuels, and to provide potential feedstock for the growing chemical industry. This paper aims to outline an integrated completion engineering and geosciences approach that was applied in the Jafurah shale gas play. The goal was to address complex unconventional reservoirs and their associated challenges, and to determine the optimum completion and fracture design. Sweet spot identification within the Jurassic Tuwaiq Mountain Formation in the Jafurah basin represents a major challenge as it requires a large number of wells drilled over a wide geographical area with high associated costs. This requires innovative drilling, completion and stimulation practices. In order to identify and maximize potential frac stages and placements, a comprehensive study was completed using an advanced workflow encompassing drilling, geophysics, geomechanics, reservoir characterization, completion and fracturing and microseismic monitoring. The targeted Jurassic Tuwaiq Mountain rocks are calcareous and interpreted to have been deposited in a restricted marine environment within an intra-shelf basin. This shale carbonate play shows a high Total Organic Content (TOC), low clay content, good matrix permeability, high gas saturation and high effective porosity. Scanning Electron microscope (SEM) images exhibit a dominant presence of organic porosity associated with the kerogen. Initial results from vertical wells drilled in the Jafurah basin proved that proppant fracturing can be successfully placed, and indicated the presence of a potential gas rich play within the same source rock. Subsequent horizontal wells were the first liquid rich/gas carbonate horizontal wells with ultra-low shale permeability in Saudi Arabia. The first horizontal wells had excellent gas production with significant amounts of condensate. By further building on experience from the drilled and stimulated wells, the lessons learned provide a foundation for the completion of future unconventional gas wells in the Jafurah basin.

There is little understanding on how the fracture networks in unconventional source plays, commonly referred as Stimulated Reservoir Volumes (SRV), grow with distance and time during the fracturing jobs and connect other offset laterals with or without hydraulically created SRVs. Understanding of this connectivity with offset wells helps on defining the distance among the laterals to avoid any potential negative impact during fracturing and production. In Jafurah field, several pads have been used to monitor pressures during the fracturing jobs (crosslinked, hybrids and slickwater) and flowbacks. This provides a unique way of measuring the fracturing network pressures at different distances for the initial life of the wells, starting from the generation of the fracture system up to pressures responses due to the production of offset wells. This paper summarizes the layout and technologies used in a series of pads to understand the connectivity among the wells. Bottom-hole and surface pressures were collected during frac and production in the pads. Also, the outer wells on the pads were monitored from offset contiguous pads. Once the pressure data was synchronized in the different events during fracturing, pressures are plotted to determine the level of pressure disturbance with time. Simultaneously, the absolute values are compared with the minimum stresses, re-opening pressures of natural fractures, and the vertical stresses from the area to determine if the fracture network is reaching the monitor wells and stimulating them. Pressures and derivative behavior are also plotted during the production of the offset wells, to see the level of interference during the initial production, and how the intensity changes as function of time. It was observed in all the pads that pressures in the monitor wells during the fracturing jobs have four periods: 1) no pressure disturbance is observed (compressibility effects); 2) pressure slowly increases up to equivalent minimum stress (closure pressure); 3) pressure continues increasing from the minimum horizontal stress up to re-opening pressure of the natural fracture systems; and 4) pressure stays above the natural frac re-opening pressure but below the vertical stresses (overburden). It can be seen that pressures in the monitor wells present a cumulative effect, suggesting a generation of fracture systems all hydraulically communicating. This paper will present the different levels of interference observed in the pads as a function of frac types, distance to the monitor wells, and existence of hydraulic fracture in the monitor area. The methodology can investigate interference in unconventional wells during the fracturing treatments and production. This approach will help in understanding how the fracture networks in unconventionals grow and connect to other offset wells.