with well write-offs, including wells that had been previously suspended pending determination as to whether the well had found reserves that could be classified as proved. The effect on exploration expenses in future periods of the $2.4 billion of suspended wells at year-end 2011 is uncertain pending future activities, including normal project evaluation and additional drilling.

     Refer to Note 19, beginning on page FS-47, for additional discussion of suspended wells.

     Income Taxes Information related to income tax contingencies is included on pages FS-43 through FS-45 in Note 15 and page FS-56 in Note 24 to the Consolidated Financial Statements under the heading “Income Taxes.”

     Other Contingencies Information related to other contingencies is included on pages FS-57 through FS-58 in Note 24 to the Consolidated Financial Statements under the heading “Other Contingencies.”

Environmental Matters

Virtually all aspects of the businesses in which the company engages are subject to various federal, state and local environmental, health and safety laws and regulations. These regulatory requirements continue to increase in both number and complexity over time and govern not only the manner in which the company conducts its operations, but also the products it sells. Most of the costs of complying with laws and regulations pertaining to company operations and products are embedded in the normal costs of doing business.

     Accidental leaks and spills requiring cleanup may occur in the ordinary course of business. In addition to the costs for environmental protection associated with its ongoing operations and products, the company may incur expenses for corrective actions at various owned and previously owned facilities and at third-party-owned waste disposal sites used by the company. An obligation may arise when operations are closed or sold or at non-Chevron sites where company products have been handled or disposed of. Most of the expenditures to fulfill these obligations relate to facilities and sites where past operations followed practices and procedures that were considered acceptable at the time but now require investigative or remedial work or both to meet current standards.

     Using definitions and guidelines established by the American Petroleum Institute, Chevron estimated its worldwide environmental spending in 2011 at approximately $2.7 billion for its consolidated companies. Included in these expenditures were approximately $1.0 billion of environmental capital expenditures and $1.7 billion of costs associated with the prevention, control, abatement or elimination of hazardous substances and pollutants from operating, closed or divested sites, and the abandonment and restoration of sites.

     For 2012, total worldwide environmental capital expenditures are estimated at $1.0 billion. These capital costs are in addition to the ongoing costs of complying with environmental regulations and the costs to remediate previously contaminated sites.

     It is not possible to predict with certainty the amount of additional investments in new or existing facilities or amounts of incremental operating costs to be incurred