CALGARY - Texas-based Wilks Brothers LLC says it is making formal the $26.1-million takeover bid for Calfrac Well Services Ltd. it proposed last week, while continuing to urge shareholders to reject a management reorganization plan.

The company, which owns U.S. oilfield services rival ProFrac Services, says it will pay 18 cents per share in an offer filed with Canadian securities regulators that will remain open until Dec. 23.

The battle for Calfrac has pitched debtholders against shareholders, with the company noting its proposed recapitalization plan made through a court-supervised Canada Business Corporations Act process has the backing of 78 per cent of holders of senior unsecured notes and will allow the company to carry on as an independent firm.

The reorganization must be supported by two-thirds of Calfrac's debtholders and shareholders in separate votes next week in order to proceed.

Earlier this week, proxy adviser Institutional Shareholder Services Inc. recommended shareholders vote down the management plan, noting that an alternate proposal promoted by Wilks offered better terms for shareholders and a better debt profile but can't be put in place without company support. It said the takeover bid mitigates the risk of having to restart negotiations with debtholders.

Calfrac, meanwhile, said in a release on Tuesday that rival proxy adviser Glass Lewis & Co. supports its reorganization as it provides shareholders with a chance to retain some value in Calfrac's future business and potentially realize a financial recovery.