Super-Critical Production From Horizontal Wells in Oil Rim Reservoirs
- S.A. Tiefenthal (Shell Intl. Petroleum Mij. B.V.)
- Document ID
- Society of Petroleum Engineers
- SPE Reservoir Engineering
- Publication Date
- November 1994
- Document Type
- Journal Paper
- 272 - 277
- 1994. Society of Petroleum Engineers
- 1.6 Drilling Operations, 5.6.4 Drillstem/Well Testing, 2.4.3 Sand/Solids Control, 5.2.1 Phase Behavior and PVT Measurements, 5.6.9 Production Forecasting, 5.5.8 History Matching, 1.6.6 Directional Drilling, 5.1.1 Exploration, Development, Structural Geology
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A model for the prediction of super-critical production rates fromhorizontal wells in oil rims is presented. The model is based on an extensionof the two-dimensional gravity drainage model for critical rates in two phasescenarios. The extended model can be used for two (gas/oil or oil/water) andthree phase (gas/oil/water) with unfavourable mobility ratios. A field examplefrom the Troll West oil rim illustrates the applicability of the model.
Horizontal drilling activity has for the last few years been on anexponentially increasing trend, but appears now to be reaching a plateau. Themain benefits of horizontal wells over vertical wells have been identified, andthese benefits are exploited as seen fit. In practice, wells are drilledhorizontally (or near horizontally) to take advantage of one or more of thefollowing features:
1. Increased exposure of reservoir rock to the wellbore (for improved inflowperformance). 2. Ability to connect laterally distributed reservoir features(e.g.: sand lenses, reservoir compartments, natural fracture systems). 3.Changed drainage geometry with well being parallel to fluid contacts.
The combination of increased exposure and the changed drainage geometry isallows horizontal wells to out-perform vertical wells in coning situations.Whereas this knowledge has been applied successfully in a number of recentdevelopments, often turning an otherwise uneconomic or marginal oil rim into aproductive field, the physical principles behind oil production in coningsituations are still not fully understood.
Analytical models based on various assumptions are available for calculatingbreakthrough times in two and three phase cases, and also for estimatingcritical rates. In practice, however, these models appear to have limitedapplicability as they fail to address the most important production phase:post-breakthrough oil, gas and/or water production. Numerical simulation hasthus become the default tool for estimating the post-breakthrough performanceof horizontal wells, even for screening purposes.
The objective of this paper is to address the physical principles governingthe postbreakthrough performance of a horizontal well in an oil rim, and topresent a model that can be used to quantify post-breakthrough productionrates.
Oil rims can be classified into two groups, depending on the fluids presentat original reservoir conditions: two phase (gas/oil or oil/water) and threephase (gas/oil/water). In principle, there should be no distinction between agas/oil case and an oil/water case. The coning behaviour will be governed bythe contrast between the two fluids, mainly in terms of density and mobility.Thus, a model developed for a gas/oil case should be equally valid for anoil/water case, provided density and mobility contrasts are similar. No furtherdistinction will be made between gas/oil and oil/water cases in this paper.
|File Size||452 KB||Number of Pages||6|