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Water injection projects in the Texas Panhandle have encountered numerous scale, corrosion, and injection well plugging problems that may be traced to chemical-biological contents and reactions in the injection water. This paper outlines the nature of these problems based on experience gained in conducting field studies and related laboratory tests.
Analyses of typical shallow supply sand and oil producing zone waters are listed. Field results of various methods of water conditioning are also included.
Discussed in detail are the merits, deficiencies, and applicability of comingling the various supply and produced waters available in this region; the types of water handling systems found to be most effective in rendering these waters suitable for injection; and the basic approaches to the types of chemical treatment required.
Economic considerations of the various methods that may be taken to solve Panhandle water problems are also included.
Water flooding in the Texas Panhandle has met with varying degrees of success in regard to oil recovery. Many injection water problems have been encountered and their solutions have also met with varying degrees of success.
Fortunately, sufficient fresh water for injection has usually been available from the Ogallala or other shallow sands. Until recently most operators have comingled this water with small initial volumes of water produced with their oil and injected the mix in a common unlined system. Severe corrosion soon led many operators to line surface and downhole pipe. Unfortunately, in many instances this merely delayed further corrosion problems since holidays or partial failure of the coatings eventually led to a concentrated corrosion attack and inevitably leaks.
Compounded with the corrosion (even when coatings were effective in stifling corrosion) other problems became apparent. Injection pressures climbed beyond those anticipated. Careful analysis of some of these "system in trouble" by the author and others closely associated with their operation revealed plugging of injection wells with either iron sulfide, calcium carbonate and sulfate, iron oxide, bacteria, oil, other organic materials, and sand or combination of two or more of these substances.
Filters were installed on many projects but they soon became ineffective or inoperative due to rapid fouling with oil, iron sulfide or oxide, sand, bacteria, etc
Inspection of pipe specimens revealed most systems were coated with deposits precipitated from the water they carried. Calcium carbonate, iron sulfide, bacterial slimes, oil, "gunky" inhibitors, and iron oxide were the deposits most universally found.
What caused these widespread water oriented problems? Why did they occur?
An examination of some representative fresh and produced water analysis (Tables 1 and 2) by experienced water experts readily reveals the causes of these problems! The water oriented problems occurred because all too frequently a trained water specialist was not consulted to review representative analyses from each specific project before it was placed in operation. "Put in a system, start water injection, and let's see what happens" has been a costly policy when followed in the Texas Panhandle.
WATERS AVAILABLE FOR INJECTION
A comparison of the fresh water analyses in Table 1, demonstrates the variation that may be encountered in each constituent of Panhandle area fresh waters.