Design of a Dislocation Well Pattern and Drilling of Shallow 3D Cluster Horizontal Wells for Development of Ultra Heavy Oil

Abstract

The Junin block in Venezuela was known as an ultra heavy oil belt reserved in extra shallow layers (950ft-1,380ft) with unconsolidated formations. A cluster wells platform drilling was required for the Field Development Program (FDP). Optimisation of the well pattern and drilling of shallow 3D cluster horizontal wells for development of ultra heavy oil are presented in this paper. A well pattern of hand-shape dislocation was forwarded to enhance effective recovery of heavy oil in diamond blind area. Optimisation of the casing programs and control of the well trajectories as well as other key performance drilling were designed. A strict anti-collision barrier design and operation steps were worked out to assure the drilling safety. The loss-resistance, anti-collapse, stick-stuck proof, lubrication and reservoir protection were put into considerations for the drilling fluid design. Recovery of heavy oil was enhanced by means of electrical heating system. Drilling challenges such as shallow target zones, big build-up rate, long horizontal sections, great friction drag and torques, and well trajectories control were experienced and settled. Especially the puzzles of well trajectories control in unconsolidated formations, great friction drag and torques of strings in large displacement long horizontal sections for subsequent operations, and the unstable wellbore were tackled. A typical well data revealed that the horizontal displacement vs. TVD ratio was as high as up to 4.5. The setting depth of surface casing and the determination of KOP were critical to the horizontal wells with large displacement in shallow layers. Pressurized combined drilling and casing-running by means of top drive overcame the drag and torque and achieved planned TD and casing setting depth. The use of electrical wireline heating rod increased the temperatures in and close to the wellbore, and compensated the radius heat loss and avoided viscosity increase of heavy oil so that the output was maintained and improved. It was the first time for successful drilling of shallow 3D cluster horizontal wells with ratio of horizontal displacement vs. TVD over 3.5 in heavy oil belt of Venezuela. The innovative palm-shape dislocation of the well pattern design satisfied the demand of reservoir development and contributed to good production gain of heavy oil.