Shunt tube deployed Open Hole Gravel Pack (OHGP) completions have been installed in the industry for about 25 years and have become widely recognized as a very reliable sand control completion technique. Some of these shunt tube gravel pack operations, are pumped with no positive surface treating pressure for a long duration of the packing operation. This paper will discuss in detail the system hydraulics and shunt tube packing process in these types of operation. The paper will review the surface and down hole gauge pumping data from a suite of shunt tube gravel packs which were pumped for sustained periods with no positive surface treating pressure. It will identify and discuss gravel packing signatures and trends that are unique to these types of operations including detailed analysis of down hole gauge data. Additionally, the paper will discuss the challenges and potential issues that can occur when executing this type of gravel pack and potential mitigation measures. Shunt tube deployed OHGP systems are designed to function in wells with small fluid weight to fracture pressure windows and as such are pumped at low rate with a viscous carrier fluid. Consequently, many of these gravel packs are pumped with no positive pump pressure as the positive u-tube pressure of the additional hydrostatic weight of the slurry in the work string is higher than the overall friction pressure in the system. This effect can have a significant impact on the job execution in several ways if not fully understood and appropriately incorporated into the pumping plan. The potential impacts which are discussed in the paper, include: Inability to monitor the downhole packing process and bottom hole circulating pressure which can result in fracturing the formation while still with no positive surface pressure. Apparent increases and decreases to the return rate which can potentially be misinterpreted as losses or gains and subsequently drive detrimental changes to the execution plan including early termination of the operation and large reductions in pump rate. Stalling of the down hole packing process when there is inadequate pressure differential to drive flow through the shunt tubes The mechanics of pumping shunt tube OHGPs without positive surface pressure has not been previously studied in depth or documented. Given the challenges with real time pumping diagnostics and post job analysis of the packing process of these jobs and the potential for misinterpretation of the data, the paper will provide a comprehensive review of this issue that can be used as a basis for designing and executed future operations.