Today, many wells all over the world are being completed with long intervals and complex completion equipment, such as limited-entry liners (LEL) and inflow control devices (ICDs). Accurate predictions and understanding of fluid placement during stimulation or injection operations through these complex completions can be quite challenging. This paper presents an integrated software technology based on research and field application for advanced completion, stimulation and fluid placement design of complex wells. The crux of the software is a novel and robust computational modeling simulator. Using innovative computational algorithms, this simulator models numerous challenging physics of acid stimulation and transient injection of multiple fluids through openhole complex completions, e.g. LEL and ICDs in long wells. LEL hole or ICD nozzle diameter, hole distributions, and packers are modeled as part of the completion while explicitly tracking multiple fluid concentrations and accounting for completion and formation pressure drops along the lateral and transient reservoir dynamics. Fundamental understanding of fluid placement is achieved through this stable and accurate computational model supported by experiments. Large-scale experiments have been performed to validate the model and understand the annular fluid displacement of multiple fluids through complex liner designs. Fluid invasion and stimulation distribution (wormhole and skin) along the lateral are computed by the simulator, which is coupled with a dynamic wormhole model. In addition to acid stimulation design, the software also provides capabilities to model various well injection processes in sandstone and carbonate reservoirs, such as scale squeezes, solvent treatments, and HF acid treatments along with corresponding productivity uplift estimates.The integration of the computational model into proprietary subsurface software is achieved through an accelerated technology delivery process involving engineering researchers, software developers/ computational scientists, and end-users in the field. The software creates a distinct advantage by giving engineers in the field the capability to quickly perform these analyses, which can lead to reduced overall development and operation costs, increased individual well productivity, and most importantly the capture of additional reserves.A case history of the model application will be presented. The model was used to design a limited-entry liner with 4 mm holes distributed non-uniformly among 12 compartments. The liner enabled successful high-rate bullhead stimulation of an 11, 500-ft lateral, resulting in reduced cost, limited risk, and elimination of the need for coiled tubing. The field data is used to validate the model predictions and calibrate model parameters.