Would You Like Good Lab Results or a Productive Well? Getting Wellbore Cleanup Testing Right!

Abstract

AbstractSoft sand wells are typically more expensive completions due to the need for sand control. The sheer cost of the wells makes the completions more high risk and increases the need for laboratory testing to validate the screen or gravel pack sizing as well as drill-in fluid selection and filtercake cleanup.Laboratory simulations of actual wellbore conditions to determine the effectiveness of wellbore cleanup treatments is quite complex. When the formation is unconsolidated and requires sand control such as screen only or gravel pack, the complexity increases further. Typical core flood equipment does not adequately confine the formation material to allow drilling and cleanup fluids to be circulated at representative shear rates and pressures over the formation face.The paper summarizes over 15 years of work to develop procedures for dynamic drill-in fluid flow testing in a screen-only or gravel pack scenario. The suite of tests has been successfully used for multiple operators in order to determine the effects of drill-in fluids with unconsolidated and consolidated formation as well as to optimize clean-up treatment and gravel pack performance. This results in selection of least damaging drill-in fluids and better filtercake removal.Dynamic flow cells have been designed to enable laboratory testing to be performed under matching wellbore conditions. This dynamic flow test method is unique because it has true slot flow that enables the filtercake to be deposited on the face of an unconsolidated formation pack. The well conditions are received from the client and the shear rate at the formation face is calculated and matched in the laboratory. Another unique aspect of the design is the ability to form the drill-in fluid filtercake on multiple test cells simultaneously.Once the drill-in fluid filtercake is established, it is equally important to be able to simulate filtercake clean up treatments under laboratory conditions. The test method allows for multiple flushes across the filtercake to simulate the entire clean-up system. The flushes may include solids-free mud, push pill, clean oil or brine, and a reactive clean-up treatment, depending upon the drill-in fluid being tested. Multiple cleanup treatments can be applied to the filtercake, again matching the shear rate and temperature as indicated by the client well conditions. When a gravel pack is present, the cell design allows the gravel pack to be placed after the filtercake is built on the formation sand. Then, the clean-up treatment is circulated to the back side of the screen. The test method also allows for extended treatment soak times, up to 10 days.