Soap sticks range in size from 5/8 inch to 2 inch in diameter (16mm to 50mm). The composition is either a hard, wax-like stick or a soft-core gel in a water-soluble gel tube. A thin, water-soluble paper shell jacket is also available. This style is popular because the stick is cleaner and does not break as easily. The most common size of a soap stick available is 1.25 inch in diameter and measures 16 inches long.
The more quickly a de-watering program is initiated the better the ultimate recovery will be from a given well bore. A well that has begun to ‘slug’ is overdue for surfactant treatment.
There is an abundance of soap stick manufacturers in the United States. No doubt some products work better than others. Our experience is that prior to abandoning the idea of using surfactant in a particular well, the operator should contact his current supplier or a new supplier and ask for help in selecting the optimum surfactant composition. The supplier will typically request basic information including accurate liquid rates and samples.
Suppliers can provide surfactants for brine or fresh water as well as varying percentages of hydrocarbons. Some users, with a higher hydrocarbon cut, achieve outstanding results by loading the Soap Stick Launcher with a surfactant foamer stick then alternately with an oil foamer stick. It should be noted that gauging the performance of a particular formula is made easier by the Soap Stick Launcher because it reduces the human factor during the test period.
Pro-Seal Lift Systems automatic Soap Stick Launchers can accommodate from 1 to 18 sticks (1.25 or 1.675 inch diameter depending on the model) in either hard or paper shell. The Launcher will also accommodate the smaller sizes as well, which are especially suited for those wells that require frequent application but with only a small amount of surfactant. Such a well will exhibit low bottom hole pressure and minimal water production. The operator should beware of dropping too much soap in a low water-production well. An alternative to using small diameter sticks is to use one-half of a hard stick in the Launcher.
HOW IT WORKS
Surfactant dissolved within formation water reduces the surface tension of the water molecules – promoting the formation of mist within the tubing. This mist is more easily carried to the surface by the up-flowing gas stream. The more quickly a de-watering program is initiated the better the ultimate recovery will be from a given well bore. A well that has begun to ‘slug’ is overdue for surfactant treatment.
Some operators choose to drop multiple soap sticks in to the well bore and then shut in the well for up to 24 hours prior to re-opening the location to flow. In this scenario, the formation responds positively, as a rule. However, the positive response is due more to the pressure and volume build-up versus any positive results from the soap sticks themselves.
This phenomenon can be explained: When one or more soap sticks fall into a non-flowing well bore, the soap sticks simply drill through the accumulated liquid located within the lower end of the tubing and sink into the rate hole without properly dissolving (just as a bar of bath soap in a bowl of water will remain undissolved for a long, long time). In addition to a waste of soap sticks, during this extended shut-in period, the well is not contributing to the bottom line.
The preferred way to introduce a soap stick into the well bore is as the well is flowing. Dropped while flowing, the soap stick will encounter the top of the water column where it will be dissolved by exposure to a bubbling, agitated, wet environment at an elevated temperature. By these three methods – mechanical action, chemical reaction, and temperature degradation – the stick will be entirely dissolved in short order.
One soap stick contains sufficient active ingredients to dilute one barrel of produced water only. Yet, it is common for one soap stick to result in the flow of 4 or 5 barrels of liquid to the surface. How so?
When introduced into the well bore correctly, the soap stick will dissolve and mix with only a limited amount of water – that water at the top of the water column – as opposed to the water lower in the tubing. The water at the top of the water column is considered to be the ‘low hanging fruit’ meaning that it is the easiest water to be blown to the surface – in mist form. Once this uppermost volume of water is discharged, the formation – thus lightened – will spit out additional barrels of water in slug form. As proof of this concept, a water analysis of this tail water will show almost no undissolved surfactant.
Dropping a soap stick, whether manually or with the Launcher, is best done while the well is flowing. However, a problem arises when the flow rate from the tubing exceeds a known maximum during the launching process. Under those conditions, the well should be shut-in for a brief period of not more than 4 minutes, preferable 2 minutes, while the soap stick is transiting to a point below the wing block. Thereafter, the well may be re-opened to flow. The reliable soap stick will fall until it encounters the top of the water column. The maximum suggested flow rate for dropping a soap stick without a mandatory, but brief, shut-in is 250 MCFD in 2-3/8″ tubing.
The only other reason to shut-in the well when using a soap stick is when a weak formation requires a pressure and volume build period. Under those circumstances, the Launcher Controller will cause the flow-control motor valve to close for the shut-in duration chosen by the operator. In this scenario, the actual launching of the soap stick is delayed until just 1 or 2 minutes prior to the re-opening of the well to flow. This Launch Delay feature is selected on the Menu Screen of the Model 9 and Model 18 Launchers.
See the Launcher Manual for more information on this and other topics.