NEW TECHNOLOGICAL DEVELOPMENTS AND METHODS FOR IMPROVING WELL PLACEMENT IN THE VINCENT FIELD, AUSTRALIA

摘要

Advanced well placement technologies were utilized from the commencement of the development of the Vincent oil field located offshore, west of Australia. The first development well was drilled in June 2007. To date, there are a total of eight bi-lateral and five tri-lateral development wells with average horizontal well lengths in the reservoir exceeding 2000 m. Geological and reservoir complexities contributed to a challenging drilling and geosteering environment, which often resulted in a number of undesired sidetracks to achieve the optimum well placement and meet pre-drill objectives. Drilling challenges included very fast penetration rates requiring immediate well placement decisions to be made, drilling windows of less than 3 m true vertical depth (TVD) in sections of wells and loss of directional control due to encountering faults and dipping stratigraphic surfaces. Deep reading azimuthal resistivity logging-while-drilling measurements were used to position wells as high as possible to top structure and away from the oil-water contact. Interpretation of top structure from directional resistivity data is complicated by interference from dipping low resistivity intra-reservoir beds. Through detailed study of azimuthal resistivity responses from previous well campaigns and collaborative interpretation between the well placement and subsurface teams, the measurement signature between top structure and intra-reservoir surfaces was able to be distinguished. Accurate, high density well surveys are critical when steering within a thin oil column. In a few earlier wells, low stationary survey sampling frequency of approximately every 30 m at the end of each drilling stand did not capture the true well trajectory and resulted in incorrect well positioning and inadvertent penetration of the gas-oil contact in one well. Subsequently, high density continuous surveys acquired while drilling were used as indicators for additional infill stationary surveys. Recently, a new processing method has been developed to integrate stationary surveys and continuous surveys in near real-time, improving wellbore placement accuracy and removing the requirement for time-consuming infill stationary surveys. In addition to the above, to overcome the drilling challenges in the Vincent field, a new steering technology has been applied which is capable of greater dog-leg severity and has further aided well placement. This new rotary steerable system is a hybrid push- and point-the-bit technology and has potentially reduced the number of sidetracks required for optimal well placement.