This study presents a methodology to define the most adequate artificial lift technique based on the method limitation itself, suitability coefficient (based on an attributes table) and economic analysis towards horizontal wells configuration. The technical limitations of each method have been determined based on physical principles and experience reported in open literature. An attribute matrix has been generated based on the information provided in open literature. A breakdown of operational and capital cost is proposed to compare the equivalent cost of each method based on how long the method will last and how often well interventaions are required. A field example is presented to demonstrate the use of the proposed methodology.
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.
As part of the stimulation plan to obtain the optimum slickwater frac design in the main source rock play in Saudi Arabia, a series of systematic trials were carried out testing different frac design parameters, such as the proppant volumes and types, and fluid & additives volumes (friction reducers, spearhead acid etc.). These trials were carefully designed in several 4-well pads across the field, comparing different designs in wells next to each other in the same pad, to allow consistency in reservoir and geology conditions allowing the trials to be conclusive. Wells were flowed back for a relatively short period of time and different production analysis techniques were used to compare the different designs against the standard. In this paper, the Normalized Initial Productivity Index of the wells was compared using the Gas, Gas Equivalent, Total Fluid Downhole Flow Rates Productivity Index (PI), and the Effective Fracture Lengths from rate transient analysis were used to help on selecting the optimum frac designs. In these trials, other important completion parameters were kept constant: the number of clusters per stage, cluster spacing, type of perforation guns, frac fluid and proppant type. The flowrates are measured using the three phase separators and the corresponding bottom-hole flowing pressures are estimated using multi-phase flow parameters, and the matched wellbore hydraulic models. The reservoir pressure is estimated from the pressure decline analysis of the frac stages along the lateral. The results show that there was almost no change in the productivity results by lowering the proppant volumes 25%. The results also show that better wells are obtained by lowering fluid volumes by 33% and decreasing the additive volumes by more than 75%. Overall, the improved PI obtained with lower proppant and fluid volumes and less additive concentrations, provided an optimized frac design that is being carried into the development phase wells. This paper helps in understanding and maximizing the productivity of the wells and optimizing the design including chemicals, to capitalize the value generation from the individual wells on the multi-well pads.
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