Using Jet Pump with DST
- 1. 12 PetroPulse Issue 4 April 2017 Hydraulic Jet Pumps Applications and Designs The actual working components of the Jet Pump—the noz- zle, throat and diffuser— are assembled in a variety of configu- rations and materials to suit the production requirements and the downhole environment. The Sliding Sleeve Jet Pump (SSJP) has become popular in particular with offshore operators. It can be run in a reverse circulation mode with a top lock or on tub- ing. Platform operators using electric submersible pumps have found that SSJPs can be run in to continue producing from a well when the ESP has shut down. The SSJP is suited for drill stem testing, because surface pumps are already in place and well production capacity is uncertain (jet pumps can operate at less than 5 percent of rated capacity without damaging the pump). How They Work Power fluid at high pressure (low velocity) is converted to a low pressure (high velocity) jet by the nozzle. The pressure at the entrance of the throat becomes lower as the power fluid rate is increased. When this pressure becomes lower than the pressure in the suction passageway, fluid is drawn in from the wellbore. The suction fluid becomes entrained with the high ve- locity jet and the pumping action then begins. After mixing in the throat, the combined power fluid and suction fluid is slowed down by the diffuser. Because the velocity is reduced, the pres- sure rises to a value sufficient to pump the fluid to the surface. Using Jet Pump in Drill Stem (DST) Applications Drill Stem Test Hydraulic Jet Pump has proven to be an asset in doing DST ef- fectively on wells which are either difficult to initiate flow or will not flow. Probably the simplest method is using the SSJP which has been designed to land and seal-off in a sliding Sleeve, thereby using the sliding sleeve as a pump receptacle. The SSJP may be locked into the sliding sleeve prior to be run into the well, or it can be wirelined in after the DST tools are run in and landed. The annulus-controlled safety valve immediately below the sliding sleeve provides additional well control. Features/Advantages • Provides lower cost drill stem tests as there is no special equipment to hook up on surface, which reduces rig time and run time (no coiled tubing or ESP cable). • Allows completely standard DST surface and subsurface hook- ups. • Provides maximum power fluid passage. • Provides large volume production capability up “full open” drill string. • Allows Jet Pump to be installed and retrieved by standard wireline procedures. • Allows well to be “kicked-off” safely. • Provides jet pump “rangeability” to test over wide range of production rates. Using the SSD jet Pump to Kick-Off a Well It may become evident, after obtaining well test data using the Jet Pump, that the well will flow if it could be “kicked-off”. With the SSJP, this can be easily done. The following steps will accomplish this: • Pump water down the casing annulus at surface pressure be- low the pressure required to open safety valve. • Continue pumping until all production fluids are circulated out of drill string; now annulus and tubing gradients are the same. • Retrieve Jet Pump with wireline tools, then run in wireline tool to close sliding sleeve & hang off over sliding sleeve. • Pump diesel or other light fluid down the drill string and spot just above the sliding sleeve. • Close the sliding sleeve with wireline tool and retrieve tools. • Rig up wellhead to flow. • Pressure-up the annulus and hold pressure to open the annul us controlled safety valve allowing well to flow. • If well does not flow, open sliding sleeve, run Jet Pump and operate with sufficient pressure to open the safety valve. Review Taha Metwally Complition Engineer Halliburton energy
- 2. PetroPulse Issue 4 April 2017 13 Third, in production fluids with high paraffin content, the Open Power Fluid system allows the circulation of heated liquids or dissolving agents through the power fluid and return lines. This will remove waxy build-ups which might hinder or halt produc- tion. A drawback to a typical Open Power Fluid system is that all of the gas must go through the pump and which could be a limiting factor regarding its use in gassy wells. The problem for piston pumps is that they have a tendency to gas lock. The problem for jet pumps is that their throats have a tendency to become choked, thereby inhibiting the production of the well’s liquids. 2- CLOSED POWER FLUID SYSTEM (PISTON PUMPS ONLY) In a closed power fluid system, an extra tubular string is re- quired for both the down hole and the surface. For downhole, the extra string is used to bring the spent power fluid back to the surface. On the surface, the extra string is for carrying the spent power fluid to the power fluid tank for re-circula- tion and re-pressurization. This requirement for an addition- al tubing string along with the associated complication of the bottom-hole design make the closed power fluid system more expensive than the open system. For this reason, the closed power fluid system is less popular and is used less than the open power fluid configuration. Since the produced fluids and power fluids are always separat- ed, the closed system has some advantage whereas the pro- duced fluids are extremely abrasive or corrosive, and where inhibitors are not used. A closed system allows the use of less exotic materials in the engine end of the pump and may extend the life of both the downhole pump and the surface power fluid facility. A closed system may also be favored slightly on marine plat- forms and in industrial or residential installations where avail- able space is scarce and at a premium. Since the power fluid conditioning and reservoir tank only need to be large enough to provide an adequate volume of power fluid to feed the mul- tiplex pump, the size of the power fluid tank is relatively small, and almost all of the produced fluid can be put directly into the flow line. TYPES OF OPERATING SYSTEMS There are two basic types of hydraulic pump systems: the open power fluid system and the closed power fluid system. In an open power fluid system, the operating power fluid mixes with the produced fluid within the down hole and then both fluids are returned to the surface in a commingled state. In a closed power fluid system, the production and operating pow- er fluids are never allowed to intermix throughout the entire system. Note: The closed power fluid system is limited to being used with piston pumps only. 1- OPEN POWER FLUID SYSTEM This system is not recommended for dewatering a gas well as the only path for the gas is through the pump. In all Open Power Fluid systems, only two down-hole fluid con- duits are required to operate the pump: one to contain the pressurized power fluid (normally the tubing) and direct it to the pump, and the other (normally the casing-tubing annulus) to contain both of the spent power fluid and produced fluid while they go to the surface. Since this is the simpler and more economical of the two systems, it is by far the most commonly used system. Besides the simplicity and economic advantage of this system, the intermingling of the power fluid and the pro- duced fluid has some other inherent advantages. First, the circulated power fluid is ideal for carrying chemical additives. Corrosion, scale, and paraffin inhibitors can be added to extend the life of the subsurface equipment. In addition, if there are emulsions in the produced fluids, emulsion breakers can be added to the power fluid stream. Second, the commingled power fluid has a diluting effect. Where highly corrosive production fluids are being lifted, the clean power fluid can reduce the concentration of the corrosive elements by approximately 50-80 percent. Where extremely viscous oil is produced, the diluting effect of the injected pow- er fluid can often reduce the viscosity enough to make lifting heavy crude more practical. Review