Content of PetroWiki is intended for personal use only and to supplement, not replace, engineering judgment. SPE disclaims any and all liability for your use of such content. A well deviated above the pay to reach further from the drill site or further into the pay formation to expose my contact area with the pay zone.
Content of PetroWiki is intended for personal use only and to supplement, not replace, engineering judgment. SPE disclaims any and all liability for your use of such content. The theoretical radius of a wellbore that would flow the same rate as a wellbore with a fracture. Effective wellbore radius is a comparison of flow improvement related back to physical radius.
Content of PetroWiki is intended for personal use only and to supplement, not replace, engineering judgment. SPE disclaims any and all liability for your use of such content. For a strict definition, a 90o deviated well. Actually the well covers a range of "highly" deviated wells (80o to 90o). In the strictest terms, the deviation is measured as 90o from vertical, but tilting bedding planes may make the deviation to the bedding planes a different judgment.
Hole cleaning is the ability of a drilling fluid to transport and suspend drilled cuttings. Throughout the last decade, many studies have been conducted to gain understanding on hole cleaning in directional-well drilling. Laboratory work has demonstrated that drilling at an inclination angle greater than approximately 30 from vertical poses problems in cuttings removal that are not encountered in vertical wells. Figure 1 illustrates that the formation of a moving or stationary cuttings bed becomes an apparent problem, if the flow rate for a given mud rheology is below a certain critical value. The most prevalent problem is excessive torque and drag, which often leads to the inability of reaching the target in high-angle/extended-reach drilling.
Multilateral completion systems allow the drilling and completion of multiple lateral boreholes within a single mainbore. This allows for alternative well-construction strategies for vertical, inclined, horizontal, and extended-reach wells. Multilaterals can be constructed in both new and existing oil and gas wells. General benefit provided by multilateral well design is barrel cost reduction. Multilaterals help to both reduce CAPEX and OPEX of the project and increase production.
The causes of mechanical pipe sticking are inadequate removal of drilled cuttings from the annulus; borehole instabilities, such as hole caving, sloughing, or collapse; plastic shale or salt sections squeezing (creeping); and key seating. Excessive drilled-cuttings accumulation in the annular space caused by improper cleaning of the hole can cause mechanical pipe sticking, particularly in directional-well drilling. The settling of a large amount of suspended cuttings to the bottom when the pump is shut down, or the downward sliding of a stationary-formed cuttings bed on the low side of a directional well can pack a bottomhole assembly (BHA), which causes pipe sticking. In directional-well drilling, a stationary cuttings bed may form on the low side of the borehole (see Figure 1). If this condition exists while tripping out, it is very likely that pipe sticking will occur.
The penetration of the reservoir is the realization of the whole purpose of drilling the well, whether a producer or an exploration well. Therefore, correct placement of the well within the target zone is of utmost importance. Designing the penetration is clearly a major multidisciplinary task involving not only the drilling team but also geologists and reservoir engineers. For some wells, a simple straight-line penetration may suffice to provide an economical flow. Sometimes the path should be brought back to vertical to assist in stimulation operations or to keep the well within a fault block.