TM 3207Penyelesaian Sumur dan Kerja UlangPR #

Nama: Muhammad Ikhsan Akbar12211073Dosen: SutopoAsisten: Wahyu Utomo12211071 Handita Reksi Dwitantra12211030 Deva Tasia Ulitha12211072Tanggal Penyerahan: 30 Maret 2015

FAKULTAS TEKNIK PERTAMBANGAN DAN PERMINYAKANPROGAM STUDI TEKNIK PERMINYAKANINSTITUT TEKNOLOGI BANDUNG2015Piston Effect The piston effect is the result of pressure changes, which occur inside the tubing string and annulus at the packer. In retrievable packer installations, pressure changes that occur inside the tubing at the packer act on the difference in areas between the packer valve area (Ap) and the tubing ID area (Ai). Pressure changes that occur in the annulus act on the difference in areas between the packer valve area (Ap) and the tubing OD area (Ao). In permanent packer installations, pressure changes that occur inside the tubing act on the difference in areas between the seal bore (packer valve, Ap) and the tubing ID area (Ai). Pressure changes that occur in the annulus act on the difference in areas between the seal bore (packer valve, Ap) and the tubing OD area (Ao). When calculating the piston effect, always consider the tubing-to-packer relationship as balanced when the packer is set. Any changes in well condition that occur after the packer is set will affect the packer-to-tubing relationship. When calculating the force due to the piston effect, it is the change in pressure rather than the absolute pressure that is important. To determine this, both initial and final well conditions need to be known. The initial conditions are those that existed when the packer was set, or when the seal assembly was stung into the packer sealbore. Final conditions are those conditions that are to be expected during production, stimulation, or well work-overs.

To calculate the length change due to the Piston Effect (L1), use this formula:

Buckling Effect The buckling effect is the most difficult of the four basic effects to under- stand. Tubing buckling will occur due to two different force distributions. One is the compressive force mechanically applied to the end of the tubing, and the other is the internal pressure that results in a force distribution on the ID area of the tubing. A mechanically applied compressive force acting on the end area of the tubing will cause tubing to buckle. When compressive force is applied to a tubing string that is, essentially, relatively flexible, the tubing will bow outward or will buckle. For example, tubing that is standing in a derrick will buckle or bow outward due to its own weight. The second force that will cause a tubing string to buckle is pressure. Pressure buckling will occur when the pressure inside a tubing string is greater than the pressure outside the tubing. The pressure within the tubing string creates a force distribution that acts over the ID area of the tubing, while pressure outside the tubing is creating a force distribution that acts over the OD area of the tubing. Because the pressure inside is higher than the pressure outside, these force distributions produce burst stresses within the tubing. The pressure within the tubing acts perpendicular to the inside tubing wall just as the annulus pressure acts perpendicular to the outside tubing wall. Because of the variance in tubing wall thickness, which can occur during the manufacturing process, the resulting burst stresses cannot be distributed evenly within the tubing. The uneven stress distribution causes the tubing to buckle. Use this formula to calculate the length change due to buckling:

Ballooning Effect The third effect, which must be considered in packer installations, is the ballooning effect. Tubing ballooning occurs when pressure is applied to the inside of a tubing string: The pressure differential creates forces within the tubing string, which are trying to burst the tubing. The burst forces created within the tubing string due to the differential pressure causes the tubing to swell. As the tubing swells, the tubing string will shorten if it is free to move. If the tubing is not free to move, the swelling will create a tension force (force) on the packer. This shortening of the tubing due to internal differential pressure is referred to as ballooning. If the pressure differential exists on the outside of the tubing string, the force created is attempting to collapse the tubing. As the tubing tries to collapse, it lengthens if it is free to move. If the tubing is not free to move, it will create a compressive force (+ force) on the packer. This lengthening of the tubing string due to collapse forces is referred to as reverse ballooning. In considering the results of ballooning and reverse ballooning, two point to consider are 1. The pressure that is responsible for ballooning or reverse ballooning is the pressure change in the tubing and/or annulus, and from the conditions that prevailed when the well was completed. The fact that a differential pressure exists between tubing and casing does not necessarily mean that ballooning exists. 2. Pressure calculations are based on changes in the surface tubing or casing pressure (applied) and changes in fluid density (hydrostatic).

Temperature Effect The last basic effect is the temperature effect. It is the only one of the four basic effects that is not pressure related: The length and force changes that occur are functions of a change in the average tubing temperature. The basic principles of expansion and contraction apply when the aver- age temperature of the tubing string is increased or decreased. When the average temperature of the tubing is decreased by injecting cool fluids, the tubing string will shorten in length if it is free to move. If the tubing string is not free to move, then a tension force will be created on the packer. When the average temperature of the tubing string is increased either by injecting warm fluids, or by producing warm oil and/or gas, the tubing will lengthen, or elongate, if it is free to move. If the tubing is not free to move, a compressive force on the packer will result, caused by the increase in the average tubing temperature. In many packer installations, the temperature effect will be the largest of the four basic effects. Because the temperature change in a tubing string occurs over the entire length of the tubing string, the change in average tubing temperature must be calculated to determine the resulting change in force or length. To calculate the average temperature of the tubing the bottom hole tem- perature and the surface temperature must be known. The following formula is used to calculate the average tubing temperature:

Use this formula to calculate the change in Force due to temperature effect:

Total Effect The four basic effects plus any mechanically applied forces are used to determine the total effect of the tubing on the packer. The method used to determine the total effect at the packer depends on the type of packer being considered for the installation and the tubing-to-packer relationship. In packer installations that permit movement of the tubing, the degree and direction of the tubing length change expected (total effect) must be determined after considering each of the four basic effects independently, then collectively. In packer installations that do not permit movement of the tubing, the degree and direction of the tubing force change expected (total effect) must be determined after considering the four basic effects independently, then collectively. The total effect is then determined by adding together each basic effect and any mechanically applied effect and can be expressed mathematically. Use this formula to calculate total length changes with slack off weight applied to packer: