Horizontal Length Optimization of Cold Production with Horizontal Wells in Extra-Heavy Oil Reservoirs

Abstract

The research block located in Carabobo area in Orinoco oil belt is an extra-heavy oil reservoir with very thick sands regarding fluvial-deltaic environment. This block is being exploited by cold production with clusters of horizontal wells. During development of this block, the cost for a horizontal well is only about 1.2–1.5 times that for a vertical well. However, its average production rate can reach 1300 B/D, about 5–8 times higher than that of a vertical well, which makes development very economically effective in this block. As for a horizontal well, the horizontal section length is a crucial parameter, which is a complicated technical and economic issue affected by reservoir geological conditions, drilling and completion technology, wellbore pressure loss, drilling cost, ground construction cost and other factors. Therefore the optimal horizontal section length is studied in this work. An analytical model was adopted to calculate the friction along the horizontal section. Then a flexible well of numerical simulation model was established to mimic the performance of cold production with different horizontal length. The results indicate that the single phase flow of extra-heavy oil in horizontal wellbore is laminar flow. The pressure drop along the horizontal section increases with the length of the horizontal section and the production pressure difference. The numerical simulation shows that with the increase of horizontal section length, the pressure drop along the horizontal section wellbore increases, and the cumulative oil production of horizontal wells increases. When the length of horizontal section exceeds 6000 ft, the pressure drop caused by friction can not be ignored, and the increasing range of cumulative oil production of horizontal well begins to decrease. This work provides the technical reference of development adjustment for this research block.KeywordsExtra-heavy oilHorizontal section lengthCold production