HOUSTON -- A tentative settlement by BP PLC covering hundreds of lawsuits stemming from the 2010 Gulf of Mexico oil spill has put the "trial of the century" on hold indefinitely, but several questions remain.

BP and lawyers for plaintiffs in the Multidistrict Litigation No. 2179 announced Friday night that they had tentatively agreed to terms that would end lawsuits covering losses by individuals and businesses, as well as medical claims from those who suffer from a variety of illnesses because of the spill.

Shortly after the announcements, Judge Carl Barbier of Louisiana's Eastern District federal court adjourned phase 1 of the trial that was scheduled to begin today. Though postponed indefinitely, the entire case has not been dismissed.

BP acknowledged that it has yet to reach a deal with the Department of Justice or state governments over the size of environmental penalties to be levied against the company. Separate litigation involving shareholder complaints is still pending in a Houston court.

The ultimate size of BP's payment to settle economic and medical damage claims is still unknown. BP says it estimates settling the cases will cost up to $7.8 billion, to be paid from a $20 billion trust the company had already set aside for its Gulf Coast Claims Facility (GCCF) process. That is much less than the $14 billion settlement many observers had expected, but the plaintiffs' steering committee in the case insists there is no ceiling on the amount BP will ultimately have to pay.

"The proposed settlement represents significant progress toward resolving issues from the Deepwater Horizon accident and contributing further to economic and environmental restoration efforts along the Gulf Coast," BP CEO Bob Dudley said in a release.

Lawyers for the plaintiffs said the terms of the proposed settlement call for an end to the GCCF process and the beginning of a court-administered procedure that would individually review all claims made against BP and determine how much money claimants are entitled to based on the evidence of damage that they offer. Two separate reviews would be set up, one for economic claims and another for medical claims, and plaintiffs would be free to participate in both.

Plaintiff's counsels Stephen Herman and James Roy said in a statement that the settlement with BP "will provide a full measure of compensation to hundreds of thousands, in a transparent and expeditious manner under rigorous judicial oversight."

"We are extremely pleased to bring justice to those harmed by the BP Gulf oil spill," their statement read.

Unanswered questions over Transocean

Aside from the unresolved federal environmental penalties and shareholder lawsuits, one other major question is left unanswered: the future legal environment for drilling in the Gulf of Mexico.

Rig operators have waited for months to hear Judge Barbier issue an opinion on the liability of Transocean, the firm that owned the Deepwater Horizon offshore rig involved in the incident.

Because it can be difficult to secure insurance for offshore oil and gas exploration, contracts for rig leases typically include indemnity clauses. Under such clauses, companies leasing offshore rigs to oil and gas companies agree not to sue in the event of an accident, and in turn, the larger oil and gas companies that lease the equipment agree not to sue the rig owners.

After the accident at the Macondo well, which killed 11 people and led to the largest offshore oil spill in U.S. history, Transocean activated the indemnity clause in its contract with BP, informing BP executives that it would not file suit for the loss of the Deepwater Horizon. The rig was destroyed in a massive inferno before sinking.

But BP instead pressed claims against Transocean, insisting that the rig owner was liable to some extent for the disaster.

Investors and analysts, in subsequent earnings reporting calls and at conferences, have been asking rig operators for clarification on the implications of BP's claim against Transocean. Offshore drilling contractors have reported that, thus far, the contracting environment has changed little from where it stood before the 2010 Gulf spill. But they admitted that they were carefully watching whether the courts would find Transocean liable in any way.

That question has yet to be conclusively answered.

In an earlier decision he rendered, Judge Barbier said that Transocean is not liable for environmental damages owed to the federal government and that the company could be held liable in the civil cases only if it can be classified in some way as an "operator" of the equipment. He declined to render his own verdict on that question, putting it off for a later date.

A Transocean representative acknowledged to EnergyWire that the broader implications for its industry pressed it to defend the indemnity clause. But the representative added that the company insists it is not liable per the facts surrounding the case itself.

Transocean's employees, the representative said, were operating according to information different from what BP or its other contractors had provided. Namely, this person said, Transocean employees were not informed of an earlier failed negative pressure test that suggested problems with the Macondo well. Full disclosure could have led Transocean workers to act differently, possibly preventing the accident, the company argues.

Transocean says the settlement announced Friday will not dissuade the company from continuing to defend itself in the manner it has in court.

"Delays or deals made by other players do not change the facts of this case and we are fully prepared to argue the merits of our case based on those facts," the company said in an emailed statement.