Simultaneous Fracturing and Drilling in Unconventional Shale Plays

By Robello Robello Samuel, March 26, 2014

Unconventional shale drilling has developed rapidly throughout the last decade. The development of substantial prospects, especially in shale gas plays, requires advanced technologies and prudent well monitoring. Many new operational challenges can be encountered because of simultaneous operations, such as drilling and fracturing nearby wells. While drilling, interaction from fractures of nearby wells can result in pressure communication and unexpected well kicks. Although the uncommon well kicks in these tight reservoirs are not severe, controlling wellbore pressures can adversely affect the efficiency of the drilling process and increase non-productive time (NPT). To prevent this problem, avoiding operational difficulty is essential when considering the positional uncertainty of the well being drilled and the fractured/fracturing wells as well as uncertainty related to fracture length and orientation. Consideration of moving boundaries between the reference wells and multiple offset wells and the associated challenges must be clearly understood. Also, during the planning stage, this can help with the design of optimal well placement as well as super fractures between wells. 

In an environment with a cluster of wells, designing and placing a well without colliding with an existing well is extremely important. It becomes more important when the offset well is fractured or in the process of being fractured. While designing such a well, it is important to consider its distance to all adjacent wells, including the fracture length and fracture orientation. 

Proper monitoring of the location and placement of new wells is important for avoiding collision with any existing well or avoiding other parameters, such as fracture length, effective oil drainage, relief well, temperature cycling, and injection well fractures. Some injection well fractures grow with time because of fracture-face plugging and thermal stresses. This becomes more complex when drilling a well in a multiple-well environment where the chances of not only the new well colliding with an existing well exist, but the possibility of interacting with other well parameters also exists. Collision with an existing well could result in loss of production and other unwanted problems; therefore, a rigorous procedure and consistent methodology are necessary to help avoid such incidents. This invention disclosure can provide the important aspects of multiwell geological objectives. Two moving boundary conditions can be present. When the reference well is analyzed, the offset well will also be moving. When the offset well is considered, the reference well will also be moving. Thus, both moving boundary conditions are considered with the analysis when calculating error and uncertainty.

Different methods can be used, including shortest distance, rule-based minimum-separation distance from the tip of the nearby well influencing factors, ratio-based minimum separation distance from the tip of the nearby well influencing factors, and minimum separation addition to the radii of the projections of the uncertainty ellipsoids of the offset well and the reference well together. A ranging factor can be used in combination with different methodologies and can be defined as ranging factor = center-to-center separation between the wells (S)/radius of the reference well + radius of the offset well.

The radius