Abstract Drilling horizontally to create a platform from which many hydraulic fractures can be propagated is proving to be an effective completion method to produce hydrocarbon from ultra low permeability sand, shale and carbonates. However optimization of these complex completions is presenting new challenges to the industry. Compared to vertical wells where open hole logging and cutting of core can be readily performed, there is frequently limited wellbore specific data available from horizontal wellbores due to the need to reduce cycle time, reduce risk, control costs and other operational concerns. In addition the target zone is rarely completely penetrated unless a decision is made to drill a pilot wellbore for the specific pupose of gathering well bore information. As a result there is inadequate wellbore specific data to perform formation evaluation and estimate rock mechanical properties. Consequently optimization of controllable completion and frac parameters is problemactic. These parameters include frac fluid type, volume, proppant type, amount, frac spacing, staging methodology, zone isolation, wellbore placement/orientation, etc., all of which can have varying effects on well production and economics. This presentation will describe the challenges engineers face and the methodologies which are being used to improve hydraulic fracture understanding and support decision making pertaining to the completion and stimulation of multi-fractured horizontal wellbores. Examples from several horizontal development targets including the Bakken and Eagle Ford will be shared in this presentation. Robert Shelley Bob throughout his 37 year career has established a specialty in hydraulic fracturing and reservoir evaluation of low permeability sand, shale and carbonates. Early in his career, he developed a diagnostic technique to predict the effects of formation discontinuities on hydraulic fracture propagation. More recently, he has focused his attention on performing completion/frac design and evlauation of multi-fractured horizontal wellbores. Along with authoring numerous SPE papers, articles and 7 patents, Bob holds a Bachelors Degree in Engineering and is a Registered Petroleum Engineer in Texas and Colorado. Prior to joining StrataGen in 2010, Bob worked for Halliburton, RTA LLC and Landmark.