Big bore, high flowrate, deep water gas wells for Ormen Lange

Abstract

Abstract Ormen Lange is Norway's second largest gas field located at a water depth of about 1000 meters, see Figure 1. The field development plan calls for a subsea solution with templates, manifolds and pipelines to be installed approximately 120 kilometers from shore. The development operator for Ormen Lange is Norsk Hydro, while A/S Norske Shell will take over operatorship at the start of production in October 2007. In addition, A/S Norske Shell will, after approval of the field development plan, be responsible for subsurface development, including drilling of the development wells. Ormen Lange's highly prolific reservoir capacity, in terms of permeability, size and pressure, presented the opportunity to consider big bore, high flowrate wells during the initial design concept. Figure 1. Ormen Lange development area. (Available in full paper) This paper describes the process of the big bore well concept selection for the Ormen Lange field, adding value to project economics, but within the boundaries of reservoir uncertainties and risks associated with each concept considered. Introduction The Ormen Lange field has a gas volume in place of about 528 GSm3, from which 397 GSm3 is recoverable (P50). The gas reserves cover a geographical area of approximately 340 km2, and the field is approximately 40 km long and 8 - 10 km wide. Norsk Hydro discovered the field in 1997. Five exploration and appraisal wells have been drilled on Ormen Lange. Reservoir targets and template locations Based on the results of the appraisal campaign, indicating a possibility for reservoir compartmentalization with partial sealing faults, the spreading of reservoir targets was concluded as the optimum reservoir drainage strategy. The target locations, as well as the appraisal targets (excluding appraisal location 6305/1-1, which is located further to the north outside the depicted area), are shown in Figure 2. To accommodate the spreading of the targets, the subsea development calls for two templates in the main production area (templates A and B), with a mutual distance of about 3 km. In addition, two more future templates are included (templates C and D). The well step-outs result in six wells with step-outs of less than 1.5 km from templates A and B and the remaining 18 wells with stepouts of maximum 2.5 km. The base case is 24 wells. See Figure 3 for template locations and well trajectories. Reservoir properties The main production area of the Ormen Lange field is at a water depth of 850 meter TVDMSL, and the single reservoir at 2705 m TVDMSL. The reservoir pressure is 289 bar while the reservoir temperature is 96 degrees Celsius. The depth reference to initial reservoir condition is 2,913 m TVDMSL. The temperature at the seabed is -2 degrees Celsius. The net reservoir height is 37.5 meters with around 500 mDarcy permeability, 27% porosity. The gas condensate ratio is 10,600 Sm3/Sm3 while the water gas ratio is 2.89 10−6. The net gross ration is 0.92.