Petition by plaintiffs and intervenor plaintiffs for discretionary review pursuant to G.S. 7A-31 and Appellate Rule 16(b) as to issues in addition to those presented as the basis for the dissenting opinion in the Court of Appeals allowed 7 December 1989. Petitions by defendants Estate of Riggan, McLeod Oil Co., Loren A. Tompkins and Adrian Simmons for discretionary review pursuant to G.S. 7A-31 and Appellate Rule 16(b) as to issues in addition to those presented as the basis for the dissenting opinion in the Court of Appeals allowed 7 December 1989.