(201c) Estimating the Drainage Area of Frac-HIT or RE-Fractured Horizontal Well

Production from unconventional (low-permeability) plays has emerged as a major source of oil and gas production in North America in the past decade. Use of horizontal wells stimulated by multiple transverse hydraulic fractures has enabled this development. To extract the most amount of hydrocarbons from a given acreage, it has become common practice to space multiple horizontal wells very close to each other. This often results in so-called “frac-hits”, i.e. a phenomenon where production from an existing well is considerably decreased due to interaction with a new adjacent well being fractured, as fractures from the new well may reach the original well’s drainage area. Production from an existing well may also not be optimal due to the original fracturing resulting in limited drainage area or due to reduction of the original fractures’ conductivity over time. This makes it appealing to re-stimulate the well via “re-fracturing” operations, to increase well productivity. For both cases – frac-hits or re-fracturing - it is important to quantify the evolution of the drainage area of such existing wells. Developing a model that accomplishes this calculation is the focus of this presentation. The objective is to develop a relatively simple methodology that can easily be used in the field. The approach taken is as follows:

• Develop computer simulations of scenarios that model drainage area variations due to frac-hits or re-fractures,
• Conduct rate-normalized pressure data analysis to look for factors that control the alteration of production,
• Predict simple algebraic relationships/equations with the help of identified factors to quantitatively predict altered performance of a fractured horizontal well,
• Verify the predicted equations by application to data from real wells.

The approach presented above attempts to combine the advantages of sophisticated simulation employing fundamentals and of simplified algebraic equations collectively described as decline curves.