Dissolvable Frac Balls: Compare the Hold Window and Clearance Endpoint

A dissolvable frac ball has to do two different jobs: maintain the required isolation during the operation and cease obstructing the intended flow path afterwards. A quotation that gives only a dissolution time does not establish both. Before ranking samples, define the required pressure-holding interval and exactly what will count as clearance.

The MOS catalogue includes Dissolvable Frac Ball Type K and other ball types. Their listed working conditions and dissolution entries are starting points for a technical enquiry. They are not a common, fully specified test protocol from which this guide can select a type for a well. No MOS field performance or comparative trial is reported here.

Name the endpoint before comparing the number

Pressure retention, passage through a seat and complete dissolution are different questions. The first concerns a ball-and-seat assembly under load for an agreed interval. The second concerns clearance through a particular opening. The third concerns the defined disappearance or dissolution endpoint. A result for one cannot silently replace the other two.

Parker's description of its dissolution calculator makes the distinction useful to buyers: it takes fluid temperature, salinity, ball size and overlap as inputs, and separately estimates passage through the seat bore and full dissolution. That is an example of how a supplier defines its own prediction. It is not a calculator for MOS materials, and no prediction was run for this article.

Write the acceptance question in the purchase record. “Holds isolation for the specified interval under the agreed differential-pressure and temperature history” is different from “passes the specified seat by the agreed observation time”. If complete dissolution is also required, define it separately, including how remaining material is assessed. The responsible completion-tool engineer must agree the actual criteria and compatible test arrangement.

This distinction also changes a rejection decision. Early loss of isolation is not a successful result merely because later clearance is rapid. Conversely, remaining material does not by itself prove failure of a passage criterion. A visual record or a mass-loss measurement can support an investigation; it does not automatically prove pressure retention or unobstructed flow through the actual assembly.

Put each result on a comparable test basis

The footnote in NOV's d-Solve data sheet ties its typical dissolution result to a particular ball diameter, brine concentration and temperature. The important purchasing lesson is the qualified basis, not a number to copy into another supplier's specification. Baker Hughes likewise identifies temperature and brine concentration as influences on its material's disintegration rate. Neither source qualifies an offered MOS type.

Use the following record to expose missing comparisons before commissioning a test or accepting a sample result. It is a proposed purchasing checklist, not a downhole operating procedure or a universal laboratory standard.

Do not convert a reported mass-loss rate into a guaranteed clearance time by a simple division. That calculation does not establish the relevant geometry, the evolution of the sample or its ability to retain pressure. If a supplier proposes a model, request its applicable material, conditions and validation against the required endpoint.

For a controlled comparison, first agree the object, conditions and endpoint, then compare the identified candidates with a qualified reference using that plan. If fluids or temperature histories differ because the applications differ, report separate application assessments rather than a universal “faster” or “better” grade. Do not fill missing method details with assumptions from a neighbouring catalogue row.

Turn the missing evidence into a purchasing decision

For an enquiry about the MOS ball range, provide the intended application, ball and seat dimensions, actual fluid information and temperature history, required differential-pressure holding interval, and the separate clearance requirement. Ask for the exact proposed type, current technical documentation and traceable test evidence against that requirement. Add sample quantity, expected order quantity, packaging and destination.

The existing catalogue lists different working and dissolving conditions. A stated working time and a stated full-dissolution time must not be assumed to describe the same fluid exposure or test. Confirm the original method and the actual offered type before using either in an acceptance specification. Do not infer a metal composition from a type letter or transfer a particle test to a finished ball.

Keep an offer on technical hold when the required holding interval or clearance endpoint is unsupported, when the test sample cannot be matched to the offered type, or when a result depends on unreported conditions. Request the missing evidence or an agreed application-specific test; do not resolve the gap by choosing the shortest catalogue time.

This guide does not approve a ball for a well, prescribe chemical activation, or guarantee that milling, retrieval or another intervention will be unnecessary. Its purpose is narrower: make the supplier's evidence comparable to the buyer's actual isolation and clearance requirements before the purchase is approved.