Water Well Journal
Issue link: https://read.dmtmag.com/i/655200
In addition to the lack of visual tur- bidity and the absence of sediment, evaluating the electrical conductance (conductivity) is an effective means of evaluating development efforts. Con- ductivity measures the combined total of inorganic and organic substances present in a liquid by measuring the ability of water to pass an electrical current. In reference to normal back- ground levels, a well still shedding sediment, drilling fluid, or other detritus will typically exhibit a much higher conductivity. While not a replacement for full chemical analysis of the well, this sim- ple field test is a handy method of track- ing the effectiveness of development efforts. Evaluating other field parame- ters including pH, alkalinity, oxidation reduction potential (ORP), and chemical signatures unique to the fluids used can also assist in tracking development efforts. The termination of development should be results-based and not just a fixed number of hours with the hope that it will be sufficient. Drilling and pump contractors should charge for the development time it takes to accomplish effective and efficient well efficiency development. With regards to rig development time, the drilling rig is almost always the most powerful and versatile piece of equipment available for at the least the preliminary development efforts. As such, the heaviest drilling fluids and clean screens or perforated casing should be the primary development objectives of rig-based development. Perhaps the greatest plague of devel- opment is it rarely is performed with a sufficient amount of energy to accom- plish the task. A drilling rig can provide a direct means of expending consider- able energy (e.g., rotation on the short axis and reciprocal along the long axis of the well casing, along with introduc- ing varying pressure regimes using such things as swab/isolation plates and air- lifting procedures) and has the greatest chance of reducing the residual debris adhering to the casing and screen. So without actually performing a visual inspection of the well prior to rig de- mobilization, it is possible to hand over to a pumping developing team a well plugged and inefficient. Along with that concern is the belief a pump alone is capable of providing a sufficient pressure differential within the well during development. This mis- assumption assumes the pump can address the entirety of the submerged section of the well and generate suffi- cient flow at a high enough entrance velocity. Even upsizing the pump often fails to generate the necessary flow to break down the filter cake on the bore- hole wall/gravel pack interface, let alone provide sufficient energy to flush the debris into and out of the well. Good Development A good development program often includes multiple methods, including both mechanical and chemical efforts. The selected program should be based on the drilling method, geology, well design, and overall completion with respect to challenges that occur during construction. Mechanical methods typically focus on delivering physical energy into the producing zones. Common mechanical methods used include swabbing/surg- ing, over-pumping, jetting, bailing, airlifting, and various isolation tools incorporating one or more of these methods in an isolated zone. Chemical methods generally target the formation and area of interaction, with selection based on the geology and specific fluids used during the drilling process. Chemicals commonly used dur- ing the development process include wetting agents (surfactants), chlorine (oxidizers), acids, and polymers such as clay dispersants or clay breakers. Delays at the end of the well building process can result in extended time and efforts due to settling out of drill fluids in the formation and the gravel pack. The development time will increase the longer the drill fluids are in the well- bore. Development is not isolated to new wells. Wells mature, meaning they be- come less efficient and economical, and DEVELOPMENT continues on page 26 DACUM Codes To help meet your professional needs, this article covers skills and competen- cies found in DACUM charts for drillers and pump installers. DO refers to the drilling chart and PI represents the pumps chart. The letter and number immediately following is the skill on the chart covered by the article. This article covers: DOB-6, 7, 8; DOF-2, 4, 5, 6; DOG-1, 3, 4, 5, 6, 9 More information on DACUM and the charts are available at www.NGWA.org. Drilling fluids remain in an active well system, impacting the production zone years after completion. WWJ April 2016 25 Twitter @WaterWellJournl