Can Wet Sand be Used for more than Building Sand Castles on the Beach?

Abstract

Abstract The amount of frac sand consumed by a single horizontal well now averages approximately 13 million pounds.  Prior to pumping the sand into a well, it must be mined, washed, sieved, stored and then transported to the wellsite before transfer to a frac blender.  Today's alternative last mile logistics systems including silos and mobile containers have lowered the cost of delivery to the wellsite, provided for a sand storage buffer at the well and have also reduced noise, dust and truck traffic associated with the delivery.  The process of drying sand after washing at an in-basin sand mine involves a combination of decanting (allowing the sand to naturally drain and air dry in a pile) followed by handling operations to feed that sand into a natural gas fired kiln. The capital expenditure for installing the kilns plus the ongoing operating expense for the drying plants can be considerable. The drying process and dry storage capacity are often limiting factors in mine output. A new method is introduced using patent pending equipment to screen, transport, deliver and meter wet sand from local mines to the frac blender, bypassing the drying process altogether.  Wet sand in this application is defined as sand with a moisture content between 1% and 10% by weight.   Operational results and benefits are compared to the current industry standard of delivering sand with a negligible moisture content. This new approach is based on the general idea that the sand is reintroduced to water in the frac fluid at the wellsite where the drying process provides no direct value to the well construction.  The many reasons why silica sand has been historically dried prior to transportation from the mine are examined in detail.  An economic analysis is included as well as a comprehensive description of how the local mine locations and next generation sand delivery systems in tandem have made this possible. A field case study is presented and data across all applicable steps in this process is compared to historical and current status quo "dry sand" delivery methods.  The case study and proof of concepts include metering techniques, novel delivery methods, new loading and screening practices as well as economic models that illustrate financial value.  One of the most significant new findings derived from this method is the definitive solution for the OSHA regulations relating to silica dust exposure from mine to the wellsite.   In addition, the benefits of this method have a positive environmental impact as billions of BTUs of energy and resultant emissions traditionally used to dry the sand can be eliminated from the process. This novel method using patent pending equipment will benefit many core areas of frac sand delivery.  Definitive solutions in the HSE field are examined as well as operational innovations and significant economic benefits. The benefits of eliminating the drying process include: Lower capital costsLower operational costsReduced regulatory complexityEnhanced plant storage efficiencyLower energy input and emissionsReduced fugitive silica dust in the air