Abstract
The use of a vertical well pattern results in productivity deficiency and poor development effect when developing buried hill reservoirs with complex properties. In this work, experiments are conducted to determine the best pattern for complex structure wells in buried hill reservoirs. Discretization is employed in an experimental method that uses unit cubic rocks with a size of 5 cm × 5 cm × 5 cm. The rocks are bonded in a spotty or reticular design to form a macroscopic model. Based on water flooding similarity criteria of fractured reservoir, an experimental model similar to a quarter of a five-spot unit in an actual reservoir is designed and manufactured. By selectively plugging wells in the model, various well patterns are established. Simulation results indicate that the vertical–vertical well pattern exhibits the fastest water breakthrough, fastest increase in water cut, and lowest recovery under the same pressure difference and well spacing. The horizontal–horizontal well pattern has the slowest water cut increase and the highest final oil recovery. For fishbone wells, this pattern facilitates an ideal development effect when the percolation direction is perpendicular to the plane determined by the mother bore and branch. When liquid rate, water cut, and recovery are considered, the horizontal–horizontal well pattern is recommended when conditions allow.
Highlights
Yu [19] compared the difference between the development effects of low-permeability reservoir in multi-fractured horizontal wells and that in fishbone wells
A buried hill reservoir features developed fractures, good connection, and thick layer [29], resulting in low productivity and poor development effect when developed with vertical wells
This paper reports on the best well pattern and development law for buried hill reservoirs through experiments
Summary
The complex structure well technique that was developed in the twentieth century can reduce water and gas coning, improve the production of thin and fractured reservoirs, and contribute to higher oil and gas production while producing lower cost and greater economic benefit, especially in cases in which vertical wells are not economical. Complex structure wells can generally be categorized into horizontal, fishbone, and multilateral wells. Fishbone well technology extends the horizontal section plane with a single horizontal wellbore to a plane with more than one horizontal wellbore, achieving a more exposed reservoir area and increasing well production [2]. Multilateral well technology improves well productivity by maximizing reservoir contact, resulting in a development with fewer wells while minimizing water and gas coning [3]. Multilateral well technology has been applied to increase the production rate per well [4]
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