Production- and Value Analysis of Hydraulic Fractured Wells (2017)
Deze MSc scriptie is geschreven door oud-stagiair Thomas Leo.
Hydraulic fracturing is a stimulation method to serve the enhancement of well productivity. The fracture creates a high conductive pathway into the formation. This improves the flow performance, bypasses damage and possibly connects additional dynamic gas. In the Netherlands, 252 wells were hydraulically fractured since 1954. This constitutes less than 10% of the amount of wells drilled in the same period. The objective of this project is to achieve more insights regarding the circumstances under which a hydraulic fracture is performed. The goal is to find a quantitative relationship that will lead to an improved performance for future fracturing campaigns.
To that end, hydraulic fracturing treatments executed on vertical gas wells have been investigated through analysis of their production behavior. A repeatable method consisting of five steps has been defined. Firstly, the critical flowrate is determined by Turner’s equation. This method has been selected to avoid modeling of huff ’n puff production behavior. The second step is the use of the Decline Curve Analysis (DCA) to predict a range of ultimate production volumes. It should be noted that there is often an absence of stabilized production trends within the production data. As such, Rate Transient Analysis (RTA) has been used to perform the final three stages. These stages consists of material balances, history matches and forecasts. Moreover, an economic evaluation to quantify the commercial effects of hydraulic fracturing is performed. With hydraulic fracturing typically featuring a production acceleration, the increment in net present value (NPV) is a robust measure to define the success of a fracturing treatment.
In technical terms out of 38 investigated fractures, a total of 37 fractures had an increment in the productivity index (PI). An average increment factor of 2.8 has been determined after the well was fractured. Properties causing the highest increment in PI are low matrix permeability and a large fracture half length. The timing of the fracturing treatment has significant impact on the economic success. The earlier a fracture is set within a well’s production life, the higher is the chance of economic success. Gas reservoirs depleted less than 35% of their initial pressure show the highest gains. By analyzing wells that are immediately fractured, it came to light that the connected dynamic GIIP has a major influence on a positive incremental NPV. Another important factor for economic success are the fracture properties. All fracturing treatments pumped with more than 100,000 kg of proppant did yield high production gains. In addition to these effects, a relationship between half length and quantity of pumped proppant has been established. Last but not least, in the recovery factors of wells that were immediately fractured, an interesting trend has been observed.