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MiniFrac / DFIT / DataFrac / Mini-Fall Off


 

MiniFrac / DFIT / DataFrac / Mini-Fall Off Related Terms

MiniFrac / DFIT / DataFrac / Mini-Fall Off, DFIT, Frac Monitoring, Surface Pressure Transient Testing, Frac

Well testing has been used for decades to determine essential formation properties and to assess wellbore condition. There are many different types of tests that can be utilized to collect this information depending on when the test is conducted, the well location, the well type, and the formation type. For the most part, conventional tests (flow/buildup or injection/falloff) have satisfied the majority of our needs. However, under certain conditions, traditional test methods are not feasible for various reasons. This is especially true for very low permeability formations that require massive stimulation to obtain economic production. For these formations, it is extremely important to establish the formation pressure and permeability prior to the main stimulation. One test that has proved to be convenient for this purpose is commonly referred to as a “Minifrac” test.

A minifrac test is an injection-falloff diagnostic test performed without proppant before a main fracture stimulation treatment. The intent is to break down the formation to create a short fracture during the injection period, and then to observe closure of the fracture system during the ensuing falloff period. Historically, these tests were performed immediately prior to the main fracture treatment to obtain design parameters (i.e.: fracture closure pressure, fracture gradient, fluid leakoff coefficient, fluid efficiency, formation permeability and reservoir pressure). However, since personnel and frac equipment were all waiting on location to perform the main treatment, the falloff period was usually stopped shortly after observing closure, before reliable estimates of formation pressure and permeability could be obtained. Since these two parameters are critical to the fracture design and for production/reservoir engineering, it seemed prudent to extend the falloff period to obtain better estimates, especially since there is little hope of gathering this information after the main stimulation. Many operators have accomplished this by simply scheduling the minifrac test well ahead of the main fracture treatment. However, predicting the falloff time required to obtain meaningful estimates of formation pressure and permeability is difficult, as it depends on having prior knowledge of the permeability, in addition to knowing the geomechanical properties of the formation. In many cases, the progress of a minifrac test can be assessed with pressure data measured at the wellhead, eliminating the need for “guessing” when sufficient data has been obtained.

The created fracture can cut through near-wellbore damage, and provide better communication between the wellbore and true formation, as illustrated in below. For this reason, a minifrac test is capable of providing better results than a closed chamber test performed on a formation where fluid inflow is severely restricted by formation damage.

Minifrac introduction


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